A generic treatment of Alismatidae in the Neotropics with special reference to Brazil

A GENERIC TREATMENT OF ALISMATIDAE IN THE NEOTROPICS WITH SPECIAL REFERENCE TO BRAZIL (*)

Robert R. Haynes (**)

Lauritz B. Holm-Nielsen (***)

R E S U M O

A iubclaiit ALLimatidae noi neotÁõpicoi e. compoita de nove &amZLúu com 11

gene-noi dai quaJj,. nove

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comentíxKtoi iobne diitAtbutcão geogná^ina doi gêmsioó. Ai

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&amLtía.

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tevantamentoi da LiteAotuAa, ou monogna^iai de ãxeai neotnapicaii — eAtão nelacionadai no inZcixi de cada tnatamznto a nZvet de ^amZlta. Ai excetentou, cotícôeà do Vnojeto Fiona Amazônica &onam de tmpontJància ductiiva pana. nono tnabalho; iem eJLai mo

podenta-moi dazeA um tnatamento genênico

completo

pana toda a negião neotnópica.

(*) This is contribution No. 75 from the Aquatic Biology Program, The University of Alabama and No. 55 from the AAU-Ecuador Project. The manuscript was prepared while RRH was a Visiting Scientist at the Botanical Institute, University of Aarhus. Herbarium research for RRH was supported in part by United States Natio­ nal Science Foundation grant INT-8219896 and by grant 11-4404 from the Danish Natural Science Research Council.

(**) Department of Biology; University of Alabama; University, AL 35486, USA.

(***) Botanical Institute; University of Aarhus; Nordlandsvej 68; DK-8240 Rissokov, DENMARK.

The Alismatidae in the Neotropics consists of nine families with 22 genera, of which nine occur in the Amazonian drainage and five genera occur iη extra-Amazonian Bra­ zil. Only two families are not present in Brazil and two additional in Amazonian Bra­ zil. The present study was undertaken as a part of the authors' work with Brazilian and other neotropical plants. The excellent collections from the Projeto Flora expedi­ tions to the Amazon region have been of decisive importance, without which a complete generic treatment for the whole region would not have been possible.

In the treatment that f o l l o w s , detailed descriptions are presented for families and g e n e r a , as well as comments on generic d i s t r i b u t i o n s . The families a r e arranged in the systematic s e q u e n c e w e a c c e p t . The genera within the families are arranged a l p h a ­ b e t i c a l l y , with no attempt to illustrate relationships. At least o n e genus per family

is illustrated, a n d , for genera that o c c u r in A m a z o n i a , at least one species is i l ­ lustrated. Important r e f e r e n c e s , such as generic r e v i s i o n s , literature s u r v e y s , or neotropical t r e a t m e n t s , a r e given at the beginning of each family treatment. All cited references a r e included in the References section.

The subclass consists mostly of aquatic or subaquatic p l a n t s , which nearly all have trinucleate pollen and lack endosperm in the m a t u r e seed. T h e development of the young endosperm mostly is of the helobial p a t t e r n .

The subclass is usually considered to be among the most primitive group of m o n o -cots (Cronquist 1968) and has been considered to closely approach the Nymphaeales and possibly to have originated from some Nymphaeales a n c e s t o r . Dahlgren and Clifford ( 1 9 8 2 ) , however, question this closeness and suggest that the "primitive characters" of the A l i s m a t i d a e which give the impression of similarity to Nymphaeales actually a r e derived and result from a parallel adaptation to the aquatic h a b i t a t .

The A l i s m a t i d a e as treated here has been widely accepted for some t i m e . It has been recognized as the order Helobiae by Lawrence (1950), the super order Alismatiflorae by Dahlgren and Clifford (1982), and the subclass Alismatidae by Cronquist ( 1 9 6 8 , 1 9 8 1 ) . Although o u r treatment of the A l i s m a t i d a e does not follow any o n e classification system, w e agree with Dahlgren and Clifford that the Triuridales should be omitted from the taxon. T h e o r d e r T r i u r i d a l e s differs from the A l i s m a t i d a e by having achlorophyllous terrestrial saprophytes with endospermous s e e d s , a b s e n c e of parietal c e l l s , and per-iclinal division in the epidermis of the n u c e l l u s . Cronquist (1968) states: "Any phyletic connection between the Triuridales and the other orders of the Alismatidae must presumably a n t e d a t e the loss of endosperm by the other o r d e r s " . This seems to

imply that although there is a relationship between the Triuridales and the orders of the A l i s m a t i d a e , there a r e enough differences to separate the Triuridales into another taxon. Dahlgren and Clifford (1982) note the order is distantly related to the A l i s m a t i d a e , but the closeness of the relationship is uncertain.

For the neotropical genera of A l i s m a t i d a e , the classification of Cronquist (1981) and Dahlgren and Clifford (1982) are remarkably similar. Cronquist differs from Dahlgren and C l i f f o r d , in separating the A l i s m a t a c e a e and Limnocharitaceae and separat­ ing the P o t a m o g e t o n a c e a e and R u p p i a c e a e . W e a r e herein following Cronquist in separat­ ing the A l i s m a t a c e a e and Limnocharitaceae and Dahlgren and Clifford in combining the Potamogetonaceae and R u p p i a c e a e .

K E Y T O F A M I L I E S O F N E O T R O P I C A L A L I S M A T I D A E

1 . Ovary compound; flower epigynous H y d r o c h a r i t a c e a e

1. Ovary simple; flower hypggynous 2 2. Flowers 10-many, arranged along one side of a flattened spadix Z o s t e r a c e a e

2. Flowers 1-many, variously arranged but without a spadix 3 3. Perianth parts absent o r , if present, of similar segments 4 3. Perianth parts present, separated into sepals and petals 8

4. Flowers all imperfect 5 4 . Flowers either all perfect or both perfect and imperfect on same plant 7

5. Stigma funnel-shaped; leaves whorled, opposite, and alternate on same plant ,... Z a n n i c h e l 1 i a c e a e 5. Stigma linear; leaves opposite or alternate, but only one arrangement on any one

plant 6 6. L e a v e s opposite, serrate; seeds areolate N a j a d a c e a e

6. Leaves alternate, entire or possibly with one or two teeth at apex; seeds ridged or

smooth but w i t h o u t a r e o l a e C y m o d o c e a c e a e 7. Plants emergent; leaves basal J u n c a g i n a c e a e 7. Plants submersed or submersed and floating; leaves cauline P o t a m o g e t o n a c e a e

8. Ovules several to many; placentation laminar; fruits dehiscent L i m n o c h a r i t a c e a e 8. Ovules 1-2; placentation basal or marginal; fruits indehiscent A l i s m a t a c e a e

A L I S M A T A C E A E Ventenat

R e f e r e n c e s : B o g i n , C. Revision of the genus S a g i t t a r i a (Alismataceae). Mem. New York B o t . Gard. 9: 179-233 ( 1 9 5 5 ) . -- Fassett, N.C. E c h i n o d o r u s in the American trop­ ics. Rhodora 5 7 : 1 3 3 - 1 5 6 , 174-212 ( 1 9 5 5 ) . — Haynes, R.R. Alismataceae. Flora de Ve­ racruz 37:1-20 ( 1 9 8 4 ) . -- Holm-Nielsen, L.B. The identity of A l i s m a boliviana Rusby ( A l i s m a t a c e a e ) . Br ittoni a 3 1 : 2 7 6- 2 7 8 (1979) . — M l c h e l i . M . Alismataceae. I n A . & C . DC. M o n o g r . P h a n . 3: 2 9 - 8 3 . ( 1 8 8 1 ) . -- Rataj, K. Revizion of the genus S a g i t t a r i a II. A n n o t . Z o o l . B o t . 7 8 : 1 - 6 1 ( 1 9 7 2 ) . -- Revizion of the genus E c h i n o d o r u s Rich. Ceskosl. Akad. V e d . 156 p p . , Prague ( 1 9 7 5 ) . — Alismataceae of Brazil. Acta Amazônica 8 : 1 - 5 3

( 1 9 7 8 ) . — A l i s m a t a c e a e . Flora de Venezuela 1 1( 2 ) : 4 3 - 8 4 ( 1 9 8 2 ) . — Rogers, G.K. The genera of A l i s m a t a c e a e in the Southeastern United S t a t e s . J. Arnold A r b o r . 64:383-420

Plants h e r b a c e o u s , with milky j u i c e , m o n o e c i o u s or m o n o c l i n o u s , annuals or peren­ n i a l s , glabrous to stellate p u b e s c e n t , s u b m e r s e d , f l o a t i n g - l e a v e d , or emergent, of fresh or brackish w a t e r s . Roots f i b r o u s , few to m a n y , septate or a s e p t a t e , at base of stem o r lower n o d e s . Stems s h o r t , e r e c t , c o r m - 1 i k e , often w i t h r h i z o m e s , the rhizomes o c ­ casionally terminated by t u b e r s , the internodes w i t h o u t t e e t h , the a p i c e s without t u r i o n s . Leaves b a s a l , sessile or p e t i o l a t e ; petiole terete to t r i a n g u l a r , mostly 2 or more times length of b l a d e , with sheathing b a s e , the sheath without a u r i c l e s ; blade

linear, l a n c e o l a t e , o v a t e to rhomboid, with or w i t h o u t pellucid markings of dots or l i n e s , the m a r g i n s e n t i r e or u n d u l a t e , the apex o b t u s e , a c u t e , or a c u m i n a t e , the base with o r w i t h o u t basal l o b e s , if w i t h o u t basal l o b e s , then a t t e n u a t e , if with basal

lobes, then t r u n c a t e , c o r d a t e , s a g i t t a t e , o r h a s t a t e , the venation r e t i c u l a t e , with parallel primary veins from base of blade to apex and reticulate secondary v e i n s . In­ florescences s c a p o s e , mostly e r e c t , rarely f l o a t i n g , vertici1 l a t e , forming racemes or the verticels branching to form p a n i c l e s , rarely u m b e l l a t e , without a subtending spathe, b r a c t e o l a t e , the b r a c t s w h o r l e d , l i n e a r , delicate to c o a r s e , smooth to p a p i l l o s e , e n t i r e , o b t u s e to a c u t e . Flowers h y p o g y n o u s , perfect or imperfect, subsessile to long p e d i c e l l a t e ; perianth a c t i n o m o r p h i c ; of 6 separate segments in 2 s e r i e s , the outer 3 s e p a l - l i k e , g r e e n , p e r s i s t e n t , erect and enclosing flower and fruit or spreading to reflexed, the inner 3 p e t a l - l i k e , d e l i c a t e , d e c i d u o u s , androecium of 6, 9, o r many free s t a m e n s , if 6 then in pairs alternating with the p e t a l s , if 9 then in 2 w h o r l s with outer whorl of 6 and inner whorl of 3, if many then s p i r a l l i n g , the anthers 2-loculed, e l o n g a t e , basifixed or v e r s a t i l e , dehiscing by longitudinal s l i t s , the pollen 5-ap-e r t u r a t 5-ap-e , g l o b o s 5-ap-e , s 5-ap-e p a r a t 5-ap-e ; gyno5-ap-ecium of 6-many fr5-ap-e5-ap-e c a r p 5-ap-e l s , th5-ap-e carp5-ap-els in 1 whorl o r s p i r a l l e d , 1-loculed, each with 1 or rarely 2 anatropous o v u l e s , the placentation b a s a l , the styles terminal or l a t e r a l , the stigma linear. Fruits achenes or rarely f o l l i c l e s , mostly n u m e r o u s . Seeds 1-few, U-shaped; endosperm helobial in d e v e l o p m e n t , absent in m a t u r e s e e d s . Type g e n u s : A l i s m a Linnaeus.

A family of 10 genera o f which E c h i n o d o r u s and Sagittaria occur in the neotropics and in A m a z o n i a . E c h i n o d o r u s has a distributional and possible evolutionary center in

the n e o t r o p i c s .

K e y t o t h e G e n e r a

1. Flowers all p e r f e c t ; fruits t e r e t e , mostly ribbed with glands between the ribs E c h i n o d o r u s 1. F l o w e r s , at least the l o w e r , imperfect; fruits f l a t t e n e d , without r i b s , often with

o n e curved wing and o n e or two glands S a g i t t a r i a

E c h i n o d o r u s Rich, ex Engelm. in A. Gray

Manual 460 ( 1 8 4 8 ) . T y p e : E c h i n o d o r u s r o s t r a t u s (Nutt.) Engelm. ( = A l i s m a r o s t r a t a N u t t . ) .

Fig. 1. A - F . E c h i n o d o r u s p a n i c u l a t u s . A , habit; B , enlargement of leaf section show­ ing n o pellucid m a r k i n g s ; C, young i n f l o r e s c e n c e ; D, f l o w e r ; E , achene without any facial g l a n d s ; F, seed. G-L. E c h i n o d o r u s b r a c t e a t u s v a r . b r a c t e a t u s . G, h a b i t ; H , enlargement of leaf section showing short pellucid lines; I, top of inflorescence showing b r a c t s ; J, f l o w e r ; K , achene w i t h one facial gland; L , seed. (A-D from H o l m - N i e l s e n , et a l . 2 7 6 0 , A A U ; E-F from H o l m - N i e l s e n , et a l . 2 2 9 5 9 , A A U ; G-H, K-L from H o l m - N i e l s e n , et a l . 7 1 5 4 , A A U ; I from H o l m - N i e l s e n , et a l . 2 2 9 7 5 , A A U ; J from H o l m - N i e l s e n , et a l . 2 2 9 7 6 , A A U . )

H e i i a n t h i u m (Engelm. ex J.D. Hook.) J.G. Smith in Britton, Manual F l . N. States, ed.

2 , 54 ( 1 9 0 5 ) .

T y p e : H e l i a n t h i u m t e n e l l u m (Mart.) Britton ex J.G. Smith. (=Alisma tenel 1 u m Mart.)

Plants m o n o c l i n o u s , annual or p e r e n n i a l , e m e r s e d , in fresh w a t e r . Roots a s e p -t a -t e . Leaves e r e c -t , emersed or s u b m e r s e d ; emersed leaves p e -t i o l a -t e , -the pe-tiole mos-tly t r i a n g u l a r , rarely t e r e t e , often with a e r e n c h y m o u s t i s s u e , the b l a d e linear to broadly o v a t e , the pellucid markings present as dots or l i n e s , or a b s e n t , the margins entire or u n d u l a t e , the a p e x a c u t e to acuminate-, the b a s e truncate to c o r d a t e ; submersed leaves mostly sessile p h y l l o d e s , the blades mostly linear to rarely o v a t e , the pellucid mark­

ings present as dots or l i n e s , or a b s e n t , the margins entire or u n d u l a t e , the apex a c u t e to a c u m i n a t e . Inflorescence e r e c t , e m e r s e d , racemose or p a n i c u l a t e , rarely u m b e l l i f o r m , the b r a c t s c o a r s e , smooth to p a p i l l o s e , o b t u s e to a c u t e . Flowers p e r f e c t , subsessile to p e d i c e l l a t e ; pedicels often elongating after a n t h e s i s , ascending to recurved; sepals h e r b a c e o u s to c o r i a c e o u s , reflexed to s p r e a d i n g ; petals w h i t e , larger than s e p a l s ; a n d r o e c i u m of 9-many stamens, the anthers versatile or basifixed, the filaments g l a b r o u s ; g y n o e c i u m of many c a r p e l s , the carpels s p i r a l l e d , 1-ovuled, the styles terminal or l a t e r a l , p e r s i s t e n t . A c h e n e s t e r e t e , often longitudinally costate and g l a n d u l a r .

A predominently neotropical genus of approximately 50 species. All but one spe­ cies o c c u r s in the n e o t r o p i c s , although two others occur in temperate and subtemperate North A m e r i c a . Rataj's treatment (1978) of the genus for Brazil included 38 species. Fifteen of these occur in A m a z o n i a .

T h e genus has been divided into two s u b g e n e r a , E c h i n o d o r u s and H e l i a n t h i u m , by Fassett ( 1 9 5 5 ) · The subgenera can be separated by subgenus E c h i n o d o r u s having versa­ tile a n t h e r s and many m o r e than 20 carpels, whereas subgenus H e l i a n t h i u m has basifixed anthers and 20 or fewer carpels.

C h a r a c t e r i s t i c s other than anther attachment and carpel number that a r e impor­ tant in the taxonomy of E c h i n o d o r u s are stamen number, fruit beak lenght and gland number and a r r a n g e m e n t , leaf s h a p e , and presence and shape o f pellucid markings in the

leaf. When viewing a leaf for pellucid m a r k i n g s , it is best to place the specimen in front of a strong desk lamp and e x a m i n e the leaves with a h a n d l e n s . This usually can be d o n e with light passing through the herbarium s h e e t , if the light intensity is strong enough and the sheet is not too thick. If pellucid markings a r e p r e s e n t , they will a p ­ pear a s light areas in the leaf tissue (see F i g . 1 , Β and H) which form dots, lines or an interconnecting network of lines separate from the venation pattern.

S a g i t t a r i a Linnaeus

S p . P I . 2 : 9 9 3. ( 1 7 5 3 ) . Gen. P I . ed. 5. 429 ( 1 7 5 4 ) . Type: S a g i t t a r i a s a g i t t i f o -l i a L.

-A C D F

F i g . 2 . A- B . Sagittaria latifolia. A, habit; Β , a c h e n e i C - E . Sagittaria guyanensis C , h a b i t ; D , transection of flower showing perfect f l o w e r ; E , achene, F. Sagit­ taria s p r u c e i . F, h a b i t indicating the inflated scape w i t h sessile to s u b s e s -sile f l o w e r s . (A f r o m H o l m - N i e l s e n & Jeppesen 1 0 6 , A A U ; Β from Haynes 7093, U N A , collected in G u a t e m a l a ; C-D from H a y n e s 8 6 3 0 , U N A ; Ε from H a y n e s 8592, UNA; F f r o m Asplund 1 4 0 1 9 , S.)

a n e n s i s (Kunth) J.G. Smith (=Sagittaria g u y a n e n s i s K u n t h ) .

Plants m o n o e c i o u s or rarely d i o e c i o u s , perennial or rarely a n n u a l , submersed, f l o a t i n g - l e a v e d , or emersed in fresh or brackish w a t e r s . Roots s e p t a t e . Stems often with r h i z o m e s , the rhizomes o c c a s i o n a11y terminated by tubers, the tubers brown, smooth. Leaves s u b m e r s e d , f l o a t i n g , or e m e r s e d , e n t i r e , sessile or p e t i o l a t e , the petioles terete to t r i a n g u l a r , the blades present or a b s e n t , with or without basal l o b e s , w i t h ­ out pellucid m a r k i n g s . Inflorescence e r e c t , emersed or f l o a t i n g , rarely submersed,

racemose or p a n i c u l a t e , rarely u m b e l l i f o r m , the bracts c o a r s e or d e l i c a t e , smooth to p a p i l l o s e , o b t u s e to a c u t e , the staminate flowers a b o v e , the carpel late b e l o w . Flowers mostly imperfect, rarely the lower p e r f e c t , p e d i c e l l a t e ; pedicels elongating after a n t h e s i s , ascending to recurved; sepals herbaceous to c o r i a c e o u s , often sculptured, reflexed in staminate f l o w e r s , reflexed to appressed in carpel late f l o w e r s ; petals w h i t e or rarely with a pink spot or t i n g e ; androecium of 7-many stamens, the filaments

linear to d i l a t e d , glabrous to p u b e s c e n t , the anthers b a s i f i x e d , linear to o r b i c u l a r ; gynoecium of many c a r p e l s , the carpels spirally a r r a n g e d , 1-ovuled. Achenes compres­ sed, n u m e r o u s , often laterally w i n g e d , g l a n d u l a r , dorsally with a conspicuous w i n g .

A predominantly Western Hemisphere genus of approximately 20 species. Bogin (1955) combined Sagittaria and Lophotocarpus, recognizing 2 subgenera, subgenus Sagit­ taria and subgenus L o p h o t o c a r p u s . The two subgenera can be separated by subgenus Sagit­ taria having ascending to reflexed sepals and mostly spreading to ascending pedicels in f r u i t , and all flowers imperfect, w h e r e a s subgenus Lophotocarpus has appressed sepals and recurved pedicels in f r u i t , and the flowers p e r f e c t .

A p p r o x i m a t e l y 12 species occur in the neotropics, Rataj (1978) recognized seven species from B r a z i l . Four s p e c i e s , Sagittaria g u y a n e n s i s , S. s p r u c e i , S . rhombifolia and S. l a n c i f o l i a , occur in A m a z o n i a .

L I M N O C H A R I T A C Ε A E Takhtajan ex Cronquist

R e f e r e n c e s : B u c h e n a u , F. B u t o m a c e a e . In E n g l . , Pflanzenr. IV. 16:1-12 ( 1 9 0 6 ) . -- M i c h e l i , M. B u t o m a c e a e . In A . & C. de C a n d o l l e , M o n o g r . P h a n . 3 : 8 4-93 ( 1 8 8 1 ) ¬ — P e d e r s o n , Τ.Μ. New species of H y d r o c l e i s , S c i r p u s , and S t e l l a r i a . B o t . T i d s s k r . 57: 38-46 ( I 9 6 I ) . -- Richard, M.L.C. Proposition d'une nouvelle famille de plantes: Les Butomees (Butomeae) . Mêm. M u s . N a t . H i s t . Paris 1:364-374 (181-5) - -- Seubert, M. B u t o m a c e a e . In M a r t i u s , Fl . B r a s . 3 ( 0 : 1 1 3 - 1 1 8 ( 1 8 4 7 ) .

Plants h e r b a c e o u s , with milky j u i c e , m o n o c l i n o u s , p e r e n n i a l s , g l a b r o u s , growing e m e r g e n t , s u b m e r s e d , or f1 oating-1eaved, in fresh waters. Roots fibrous, few to many, a s e p t a t e , from a stout rhizome or stolon. Stems f l e s h y , e r e c t , unbranched, the inter-nodes without spinulose t e e t h , the tips without turions or t u b e r s . Leaves basal o r a l ­ t e r n a t e , p e t i o l a t e ; petioles terete to t r i a n g u l a r , mostly 3 or more times length of b l a d e , with sheathing b a s e , the sheath without a u r i c l e s , the infravaginal scales a b

-s e n t ; blade-s o r b i c u l a r to l a n c e o l a t e , without pellucid m a r k i n g -s , the margin-s entire, the apex o b t u s e to r o u n d - a c u t e , the base c o r d a t e to a t t e n u a t e , the venation reticulate, with parallel primary veins from base o f blade to apex and reticulate secondary v e i n s .

Inflorescence s c a p o s e , erect to f l o a t i n g , t e r m i n a l , an involucrate u m b e l , without sub­ tending s p a t h e , the involucre of few to several b r a c t s , the bracts o v a t e , m e m b r a n o u s , a c u m i n a t e . Flowers h y p o g y n o u s , p e r f e c t , p e d i c e l l a t e ; perianth a c t i n o m o r p h i c , of 6 sep­ arate segments in 2 series, the outer 3 sepal-like, persistent, mostly erect and enclos­

ing flower and f r u i t , the inner 3 petal-like, usually delicate, deciduous, androecium of 6-many stamens, separate, the anthers 2-loculed, basifixed, dehiscing by longitudinal s l i t s , the pollen 3_7 aperturate, globose, separate; gynoecium of 3-many separate or

basally coherent c a r p e l s , the carpels 1-loculed, each with numerous anatropous ovules, the placentation laminar the styles short or a b s e n t , the stigma linear. Fruit a f o l ­ l i c l e , dehiscing a d a x i a l l y . Seeds n u m e r o u s , glandular pubescent or c o s t a t e , U-shaped; endosperm helobial in d e v e l o p m e n t , absent in the m a t u r e seed. Type: L i m n o c h a r i s Humboldt 6 Bonpland.

A family of three g e n e r a , two of w h i c h , L i m n o c h a r i s and H y d r o c l e y s , occur in the n e o t r o p i c s . T h e family is considered to be among the primitive monocots by the presence of many separate c a r p e l s , many s t a m e n s , and laminar p l a c e n t a t i o n . There has been c o n ­ siderable confusion as to the systematic position of the genera here accepted to con­ stitute the L i m n o c h a r i t a c e a e . Lawrence (1951) and Hutchinson (1959) have combined these genera with B u t o m u s to form an enlarged family Butomaceae, Dahlgren and Clifford (1982) and Pichon (1946) combined these genera with the Alismataceae leaving the Butomaceae as monotypic with B u t o m u s , and Cronquist (1968) has separated the three f a m i l i e s . W e a r e following Cronquist and separating the Limnocharitaceae from the Butomaceae by the Limnocharitaceae possessing lactiferous d u c t s , leaves with petioles and expanded b l a d e s , caduceous p e t a l s , campylotropus o v u l e s , and seeds with curved e m b r y o s , w h e r e a s these characteristics a r e absent in the B u t o m a c e a e . T h e Limnocharita­ ceae can be separated from the A l i s m a t a c e a e in having numerous ovules per carpel with

laminar placentation and dehiscent f r u i t s , whereas the Alismataceae have 1-few ovules per carpel with basal placentation and indehiscent f r u i t s .

K e y t o t h e G e n e r a

I. Carpels 3 - 8 , linear-lanceolate, blades about as broad as long; styles present. H y d r o c l e y s 1 . Carpels numerous, semicircular; blades much longer than broad; styles absent

L i m n o c h a r i s

H y d r o c l e y s Richard

Mêm. M u s . N a t . H i s t . 1:368 ( 1 8 1 5 ) · Type: H y d r o c l e y s c o m m e r s o n i Rich.

V e s p u c c i a Pari., Nuov. Gen. Sp. Monocot. 55 ( 1 8 5 4 ) . Type: V e s p u c c i a h u m b o l d t i i P a r i . , n o m . illeg. ( = S t r a t i o t e s n y m p h o i d e s Willd. = H y d r o c l e y s n y m p h o i d e s (Wllid.)

F i g . 3. A - D . H y d r o c l e y s n y m p h o i d e s . A , h a b i t ; B , longitudinal section of flower i l ­ lustrating two series of stamens and many s t a m i n o d i a ; C, f r u i t , the one on the right opened to illustrate the laminar p l a c e n t a t i o n ; D, seed w i t h glandular p u ­ b e s c e n c e . E-F. H y d r o c l e y s m o d e s t a . Ε , habit illustrating submersed linear and floating elliptical l e a v e s , flowers w i t h petals as l o n g a s or slightly longer than s e p a l s ; F, seed with, glandular p u b e s c e n c e . (A-D from living material cultivated at the'AAU green h o u s e s ; E-F from M a c e d o 2 2 7 1 , S, collected in B r a ­ zil.)

Buchenau) .

Plants s u b m e r s e d , w i t h floating l e a v e s . Stems s h o r t ; stolons often p r e s e n t , terete. Leaves b a s a l , floating or s u b m e r s e d , the submersed sessile p h y l l o d i a , the floating l o n g - p e t i o l a t e , the petioles t e r e t e , s e p t a t e , w i t h a sheathing b a s e , the blade orbicular to o b l o n g - l a n c e o l a t e , the apex m u c r o n a t e to o b t u s e , the base rounded to c o r ­ d a t e . Inflorescence of few to numerous f l o w e r s , terminating a long septate s c a p e , o c ­ casionally proliferating with leaves and s t o l o n s , the scapes few to many peduncles t e ­ r e t e , s e p t a t e ; bracts elliptic to l a n c e o l a t e , d e l i c a t e , s e p a r a t e , shorter than pedicel subtended. Flowers long p e d i c e l l a t e , the pedicels c y l i n d r i c , t e r e t e ; sepals g r e e n , c o r i a c e o u s , e r e c t , l a n c e o l a t e , w i t h or without a m i d v e i n , the apex c u c u l l a t e ; petals y e l l o w to w h i t e , d e l i c a t e , o b l o n g - o b o v a t e to o r b i c u l a r , f u g a c i o u s , erect to spreading, longer than to shorter than s e p a l s ; stamens 6-many, in 1-several s e r i e s , the outer often s t e r i l e , the filaments linear or l a n c e o l a t e , f l a t t e n e d , the anthers linear; c a r ­ pels 3-8, terete, linear-lanceolate, basally scarcely cohering, attenuate into the s t y l e , the style curved inward, papillose at a p e x . Fruits m o r e or less t e r e t e , linear-l a n c e o linear-l a t e , m e m b r a n o u s , w i t h o u t dorsalinear-l f u r r o w s , dehiscing alinear-long the inner m a r g i n s . Seeds n u m e r o u s , sparsely to densely glandular p u b e s c e n t .

A genus of five s p e c i e s , all native to Central and South A m e r i c a . Four species a r e known from B r a z i l , two of these H y d r o c l e y s nymphoides and H . p a r v i f l o r a , occur in Amazon ia.

L i m n o c h a r i s Humboldt S Bonpland

P I . A e q u i n o c t . 1:116 ( 1 8 0 8 ) . T y p e : L i m n o c h a r i s e m a r g i n a t a Humb. ε Bonpl., non. i11 e g . ( = A l i s m a f l a v a L. = L . f l a v a (L.) B u c h e n a u ) .

Plants emersed. Stems s h o r t , r h i z o m a t o u s ; stolons o c c a s i o n a l , e r e c t . Leaves b a s a l , e m e r s e d , long p e t i o l a t e ; petiole t r i a n g u l a r , a s e p t a t e , often with a e r e n c h y m a ; blade lanceolate to o v a l , the apex a c u t e to round, the base a c u t e to c o r d a t e . Inflores­ c e n c e s of 1-many f l o w e r s , terminating an e l o n g a t e , a s e p t a t e s c a p e , occasionally prolif­ e r a t i n g , the scapes to c a . 10 in n u m b e r ; peduncles shorter than to equal the length of p e t i o l e s ; bracts s e p a r a t e , delicate throughout, shorter than pedicel subtended. Flowers long p e d i c e l l a t e , the pedicels somewhat d i l a t e d , often w i n g e d , often inflated, trigon­ o u s ; sepals g r e e n , broadly o v a t e , o b t u s e , a p p r e s s e d ; petals y e l l o w , f u g a c i o u s , ovate to s u b o r b i c u l a r , longer than the s e p a l s ; stamens m a n y , the outer ones often s t e r i l e , the filaments l i n e a r , f l a t t e n e d , the anthers linear; c a r p e l s 1 5 - 2 0 , laterally compressed, vertici1 l a t e , scarcely coherent at b a s e , the style a b s e n t , the stigma e x t r o s e . Fruits laterally c o m p r e s s e d , s e m i c i r c u l a r , scarcely c o h e r e n t , m e m b r a n o u s , dorsally furrowed, dehiscent internally. Seeds n u m e r o u s , transversely m u i t i c o s t a t e .

A neotropical genus of two s p e c i e s , L i m n o c h a r i s f l a v a and L. l a f o r e s t i ; both spe­ cies occur in A m a z o n i a . One s p e c i e s , L. f l a v a , has been introduced into the Asian t r o p i c s .

F i g . 4 . Α - E . L i m n o c h a r i s f l a v a . A , habit illustrating the inflated peduncles and t r i a n g u l a r , winged p e d i c e l s ; B , inflorescence; C , longitudinal section of f l o w ­ er w i t h two circles of stamens and two circles of s t a m i n o d i a ; D, fruit w i t h seeds dropping o u t ; E , seed. F-K. L i m n o c h a r i s l a f o r e s t i . F-G, habit i l l u s ­ trating typical short non-inflated peduncles and short p e d i c e l s ; H , i n f l o r e s ­ c e n c e ; I, longitudinal section of flower illustrating one circle of stamens and no staminodia J, f r u i t ; K , seed. ( A - B , D-E from H o l m - N i e l s e n 2 2 9 9 1 , A A U ; C. from H o l m - N i e l s e n , et a l . 2 8 8 3 , A A U ; F-G from Spruce 6 4 5 2 , Κ ; Η from Haynes 8 3 3 8 , U N A ; I-K. from D a v i d s e 3 8 2 0 , UNA.)

W i l d e r

(1974)

notes that the ultimate bud of the inflorescence of L i m n o c h a r i s f l a v a always develops into a vegetative bud. This vegetative bud produces a vegetative c o m p o n e n t . When the inflorescence is m a t u r e and the fruits have f a l l e n , the peduncle of the inflorescence falls to the s i d e . A new v e g e t a t i v e shoot will arise from the v e g e t a t i v e c o m p o n e n t of the m a t u r e inflorescence. This vegetative shoot will grow into 3 new erect plant.

H Y D R O C H A R I T A C E A E A . L . Jussieu

R e f e r e n c e s : A n c i b o r , E. Systematic anatomy of vegetative organs of the H y d r o -c h a r i t a -c e a e . J. L i n n . S o -c , B o t . 78:237-266 (and mi-crofi-che) ( 1 9 7 9 ) . -- Cook, C.D.K. Pollination m e c h a n i s m s in the H y d r o c h a r i t a c e a e . p p . 1 - 1 5 In J.J. Symoens, et a l . Stud­ ies on A q u a t i c V a s c u l a r P l a n t s . Brussels ( 1 9 8 2 ) . — Cook, C.D.K. & R. Lüond. A revi­ sion of the genus H y d r i l l a (Hyd rocha ri taceae). A q u a t i c B o t .

13:485-504 (1982).

— C o o k , C.D.K. and K. U r m i - K o n i g . A revision of the genus L i m n o b i u m including H y d r o m y s t r i a

( H y d r o c h a r i t a c e a e ) . Aquatic B o t . 17:1-27 ( 1 9 8 3 ) . -- A revision of the genus E g é r i a (Hydrocharitaceae) . A q u a t i c B o t . 19:73-96 ( 1 9 8 4 ) . -- A revision of the genus O t t e l i a ( H y d r o c h a r i t a c e a e ) . 2. The species of Eurasia, Australasia and America. Aquatic Bot. 20:131-177 ( 1 9 8 4 ) . -- Diaz-Miranda, D. , D. Philcox, and P. Denny. Taxonomic clarifica­ tion of L i m n o b i u m Rich, and H y d r o m y s t r i a G.F.W. Meyer (Hydrochari taceae). J. Linn. S o c , Bot. 83:31 1-323 ( 1 9 8 1 ) . — Hartog, C. den. The Sea-grasses of the World. North-Holland P u b l . C o . , A m s t e r d a m 275 pp + 31 p i . ( 1 9 7 0 ) . -- Hunziker, A . T . H y d r o m y s t r i a l a e v i g a t a

(Hydrocharitaceae) en el c e n t r o d e A r g e n t i n a . Lorentzia 4 : 5 - 8 ( 1 9 8 1 ) . — Observatiõnes biolog icas y taxonomicas sobre H y d r o m y s t r i a l a e v i g a t a (Hydrocharitaceae). Taxon 3 1: 4 7 2 ¬ 477 ( 1 9 8 2 ) . — Kaul, R.B. Floral morphology and phylogeny in the Hydrocharitaceae. Phytomorphology 18:1335 ( 1 9 6 8 ) . Lowden, R.M. An approach to the taxonomy of V a l -l i s n e r i a L. ( H y d r o c h a r i t a c e a e ) . Aquatic B o t .

13:269-298 ( I 9 8 2 ) .

-- S t . J o h n , H. M o n o ­ graph of the genus E l o d e a (Hydrocharitaceae). Pt. 1 . Res. Stud. State Coll. Wash. 30: 19-44 ( 1 9 6 2 ) . — Pt. 2. Caldasia 9:95-113 ( 1 9 6 4 ) . -- Pt. 3. Darwiniana 12:639-652

(1963). — Pt. 4. Rhodora 6 7 : 1 - 3 5 , 155-180 (1965).

Plants h e r b a c e o u s , without milky j u i c e , m o n o e c i o u s , d i o e c i o u s , or m o n o c l i n o u s , annual or p e r e n n i a l , g l a b r o u s or p u b e s c e n t , entirely submersed, or with both submersed and floating l e a v e s , or with submersed stolons and emergent l e a v e s , in f r e s h , b r a c k i s h , or m a r i n e w a t e r s . Roots f i b r o u s , few to m a n y , a s e p t a t e , at nodes or bases of stems. Stems either r h i z o m a t o u s , creeping with an abbreviated erect axis at the n o d e s , or e r e c t , leafy, e l o n g a t e , without teeth or t u b e r s , and rarely with turions. Leaves b a s a l , a l t e r n a t e , o p p o s i t e , or w h o r l e d , entire or s e r r a t e , sessile or p e t i o l a t e , 1-many-v e i n e d , the stipules sometimes p r e s e n t , forming a tubular sheath around the stem, the venation paral lei , connected by perpendicular or ascending c r o s s - v e i n s , the infravaginal scales m e m b r a n o u s . Inflorescence a x i l l a r y , t e r m i n a l , or s c a p o s e , solitary or c y m o s e ,

subtended by a spathe consisting of a bifid bract or a pair of opposite b r a c t s , the spathe often p e r s i s t e n t , sessi1e or p e d u n c l e d , often ridged or w i n g e d . Flowers epig-y n o u s , imperfect and often with rudiments of the opposite sex or p e r f e c t , actinomorphic or rarely slightly z y g o m o r p h i c ; perianth s e p a r a t e , rarely 3, mostly 6, then differen­ tiated into sepals and p e t a l s , the sepals mostly g r e e n , v a l v a t e , p e r s i s t e n t , the petals mostly c o l o r e d , imbricate or c o n v o l u t e , d e c i d u o u s ; a n d r o e c i u m w i t h stamens absent or 2-many in 1 or more w h o r l s , the inner often s t a m i n o d i a l , the anthers basifixed, 2-loculed, dehiscing by parallel vertical s l i t s , the filaments s l e n d e r , rarely a b s e n t , the pollen s p h e r i c a l , rarely a d n a t e into slender c h a i n s ; gynoecium w i t h carpels 0 or 2-6, u n i t e d , the ovary l i n e a r , l a n c e o l a t e , or o v a t e , u n i l o c u l a r , the ovules n u m e r o u s , b i t e g m i c , a-n a t r o p o u s , the placea-ntatioa-n parietal or the parietal zoa-nes ill-defia-ned aa-nd placea-ntatioa-n then l a m i n a r , the style f i l i f o r m , the stigmas equal the c a r p e l s . Frui' b e r r y - l i k e , s u b m e r s e d , linear, lanceolate or o v a t e , opening by decay of the p e r i c a r p . Seeds m a n y , fusiform, e l l i p t i c , o v a t e , or g l o b o s e ; testa s m o o t h , p a p i l l o s e , or spiny; embryo s t r a i g h t ; endosperm helobial in d e v e l o p m e n t , absent in m a t u r e seed.

A family of about 16 genera and 100 s p e c i e s , indigenous primarily in waters of the tropical and subtropical regions of the w o r l d . Eight g e n e r a , E g é r i a , E l o d e a , H a l o p h i l a , H y d r i l l a , L i m n o b i u m , O t t e l i a , T h a l a s s i a , and V a l 1 i s n e r i a , occur in the neo-t r o p i c s . T w o of neo-these g e n e r a , H a l o p h i l a and T h a l a s s i a , are marine spermaneo-tophyneo-tes; neo-the remainder occur in fresh to slightly brackish w a t e r . L i m n o b i u m and E l o d e a occur in Amazon ia.

T h e H y d r o c h a r i t a c e a e are most closely related to the Butomaceae by the modified laminar placentation and lack of lactiferous d u c t s . The family is unique among the A l i s m a t i d a e in having united carpels and an inferior o v a r y .

K e y t o N e o t r o p i c a l G e n e r a o f H y d r o c h a r i t a c e a e

1. Plants of m a r i n e h a b i t a t ; pollen grains adhering in moniliform chains 2 1. Plants of fresh or slightly brackish w a t e r s ; pollen grains separate 3 2. Leaf-bearing branches arising from rhizome at each internode; styles 3-5 ; fruit

smooth or ridged, not e c h i n a t e , dehiscing by pericarp decay h a l o p h i l a 2. Leaf-bearing branches arising from rhizome at distances of several internodes;

styles 6-8; fruit e c h i n a t e , dehiscing into 6-8 irregular valves T h a l a s s i a 3. Stems elongate (greater than 3 c m ) , erect; leaves cauline, whorled h 3. Stems short (less than 2 c m ) , or if elongate, then stoloniferous; leaves basal 6

4 . Leaves w i t h prickles along lower surface of m i d r i b ; infravaginal scales fringed with

orange-brown marginal hairs H y d r i l l a 4. Leaves w i t h o u t prickles along lower surface of m i d r i b ; infravaginal scales e n t i r e ,

or if f r i n g e d , the marginal hairs c l e a r , not orange-brown 5

5. Whorls with 3-4 leaves per node El o d e a 6. Stems stoloniferous, floating on surface or suspended in water; leaves with a e

-renchyma along lower s u r f a c e ; peduncle mostly short (less than 5 cm) L i m n o b i u m 6 . Stems short, rooted in subtrate; leaves without aerenchyma along lower surface;

peduncle mostly e l o n g a t e (more than 5 cm) 7 7. Leaves petiolate; spathe winged or ribbed O t t e l ia

7. Leaves sessile; spathe without wings or ribs V a l l i s n e r i a

E g é r i a Planch.

A n n . S c i . N a t . B o t . s e r . 3. 1 1 : 79. 1849. Type: E g é r i a d e n s a Planch.

Plant d i o e c i o u s , p e r e n n i a l , g l a b r o u s , s u b m e r s e d , in fresh w a t e r s , propagated by seeds or stem f r a g m e n t s . Roots s m o o t h , without root h a i r s , s l e n d e r , p a l e , from lower n o d e s . Stems e r e c t , branched or unbranched. Leaves w h o r l e d , 1-veined, serrate, the midrib w i t h o u t dorsal p r i c k l e s . Inflorescences a x i l l a r y , solitary; staminate spathes s e s s i l e , funnelform to broadly t u b u l a r , 2-4-flowered; carpel late spathes cylindric, split half-way down o n e s i d e , 1-flowered. Flowers impertect; staminate flowers projec­ ted to surface of w a t e r by slender e l o n g a t e hypanthium b a s e , the sepals 3, herbaceous, g r e e n , the petals 3, membraneous, white, ca. 3 times size of sepals, the stamens 9, d i s t i n c t , the a n t h e r s l o c u l i c i d a l , the filaments glandular papillose a b o v e , the nectary canal c e n t r a l , s m a l l , 3-lobed; carpel late flowers projected to surface of water by slen­ der e l o n g a t e hypanthium b a s e , the sepals 3, herbaceous, green, the petals 3, membranous, w h i t e , c a . 2 times as long as sepals, the staminodia 3, the ovary unilocular, theovules n u m e r o u s , the placentation p a r i e t a l , the stigma 3-lobed, the lobes linear. Fruits cy­

lindric, many seeded. Seeds r a r e , f u s i f o r m , b e a k e d , the testa m u c i l a g i n o u s .

A genus of 2 species, E g é r i a d e n s a and Ε. n a j a s , which are native to the neotrop­ ics. Both species occur in Brazil but neither o n e is known from A m a z o n i a . One species, E . d e n s a , has been introduced into the United States of America and Europe where, at least in the U S A , it has b e c o m e a problem w e e d .

T h e two species can be separated by E g é r i a d e n s a generally being a larger plant. For e x a m p l e , the leaves of E . d e n s a are 1.7 mm or more wide whereas those of E . n a j a s are less than 1.4 mm wide. A l s o , filaments of E . d e n s a are clavate, whereas those of E . n a j a s are 1inear.

E l o d e a Michx.

F l . B o r . - a m e r . 1:20 ( 1 8 0 3 ) . Type: E l o d e a c a n a d e n s i s Michx.

A n a c h a r i s R i c h . , M e m . C I . S c i . M a t h . Inst. N a t l . France

12(2):7,61

( l 8 l 4 ) . T y p e : A n a c h a r i s c a l 1 i t r i c h o i d e s Rich.

F i g . 5 . A - I . L i m n o b i u m laevigatum. A , h a b i t sketch w i t h emersed and floating l e a v e s ; B , enlargement of aerenchyma on lower surface of floating l e a f ; C, staminate f l o w e r ; D, longitudinal section of staminate flower showing fusion of fila­ m e n t s ; E , c a r p e l l a t e f l o w e r ; F, longitudinal section of carpellate f l o w e r ; G, f r u i t ; H , seed w i t h echinate t e s t a ; I, e m b r y o . J-N. Elodea g r a n a t e n s i s . J, habit sketch w i t h attached flower and attached f r u i t ; K , enlargement of node showing the n u m b e r of leaves per whorl and f r u i t ; L, flower; M , seed; N, embryo. (A-F from H o l m - N i e l s e n & J e p p e s e n 9 2 , A A U ; G-I from H a y n e s 8 2 8 6 , U N A ; J-K, M-N from Clark 6 5 6 7 , A A U ; L from B r a n d b y g e , et a l . 3 6 1 4 9 , A A U ) .

E l o d e a R i c h . , M é m . C l . S c i . M a t h . Inst. N a t l . France

1 2 ( 2 ) : 7 , 61

(1814). T y p e : E l o d e a g u y a n e n s i s Rich.

D i p l a n d r a B e r t e r o , Mercúrio Chileno

13:612

(1829). T y p e : D i p l a n d r a p o t a m o g e t o n B e r t e r o .

P h i l o t r i a Raf., Amer. Monthly Mag. & Crit. Rev. 2:175 (1818) . Type. Same as E l o d e a Michx.

U d o r a Nutt., Gen. N. Amer. f 1 . 2:242 ( 1 8 1 8 ) . Type: Same as E l o d e a Michx.

Plants dioecious or m o n o c l i n o u s , p e r e n n i a l , g l a b r o u s , submersed, in fresh w a t e r s , propagated by s e e d s , stem fragments or t u r i o n s . Roots s m o o t h , s l e n d e r , p a l e , un-branched. Stems e r e c t , rooting at lower n o d e s , branched or unun-branched. Leaves whorled or rarely o p p o s i t e , s e s s i l e , linear to l i n e a r - l a n c e o l a t e , 1-veined, serrate, the midrib without a dorsal p r i c k l e , the whorls with 3-7 leaves. Inflorescences axillary, sol­

itary; spathes perfect o r imperfect, s e s s i l e , usually narrowed toward b a s e , cylindric to el 1iptic-spatulate, I-flowered. Flowers perfect or imperfect, usually projected to surface o f w a t e r by the elongating hypanthium b a s e ; sepals 3 , herbaceous, green; petals 3, membranous, white to pale blue, elliptic, clawed; stamens 3 - 9 , or reduced to 3 stam-inodia, the anthers oblong to e l l i p s o i d , the filaments subulate to lanceolate, sepa­ rate o r the 3 inner united halfway to apex; carpels 3, the locules 1 , the placentation p a r i e t a l , the styles 3, the stigmas 3, bifid. Fruit ovoid to lance-ellipsoid, beaked; seeds 3 - 8 , cylindric to fusiform, glabrous to hirsute.

A W e s t e r n H e m i s p h e r e genus of 13-14 species separated into two subgenera, E l o d e a and A p a l a n t h e . The subgenera can be separated by subgenus E l o d e a having imperfect flow­ e r s , the staminate flowers with 69 stamens, and some filaments united. Subgenus A p a -l a n t h e has perfect f-lowers with three stamens, these having separate fi-laments. Two s p e c i e s , representing both s u b g e n e r a , occur in the n e o t r o p i c s . O n e s p e c i e s , E . g r a n a -t e n s i s , occurs in Brazil, including Amazonia.

T h e taxonomy o f E l o d e a is based on differences in floral structure. Without flow­ e r s , t h e r e f o r e , plants a r e difficult at best to d e t e r m i n e . Care should be taken in all cases to collect only flowering s p e c i m e n s .

H a l o p h i l a Thouars

Gen. N o v . M a d a g a s c . 2 ( 1 8 0 6 ) . Type: H a l o p h i l a madagascarensis Doty et Stone.

Plants m o n o e c i o u s or d i o e c i o u s , annual or p e r e n n i a l , glabrous or pubescent, e n ­ tirely s u b m e r s e d , in marine w a t e r s . Stems of two t y p e s , the lower rhizomatous, the

lateral erect and f o l i a c e o u s ; rhizome m o n o p o d i a l , c r e e p i n g , rooting at the n o d e s , with 1-few unbranched roots covered with fine root-hairs, the nodes with 2 scales, one of which surrounds the rhizome and the other subtends a l a t e r a l , often undeveloped, folia­ ceous s h o o t ; lateral shoot 1-4Q mm long, often with a pair of scales midway or higher on the s t e m , a second lateral shoot often developing from the axillary bud between the leaves, the second shoot producing a pair of leaves and the inflorescence. Leaves

mostly in terminal pairs or p s e u d o w h o r l s , rarely d i s t i c h o u s , sessile or p e t i o l a t e , lin­ ear to o v a t e , e n t i r e o r s e r r u l a t e , mostly g l a b r o u s , rarely pubescent. Inflorescence of 1 or rarely two f l o w e r s , dioecious or rarely m o n o e c i o u s ; spathe of 2 sessile b r a c t s , the bracts m e m b r a n o u s , elliptic to o v a t e , o v e r l a p p i n g , s e p a r a t e , a c u t e to e m a r g i n a t e , entire or rarely c i l i a t e to s e r r u l a t e , k e e l e d , the keel often s e r r u l a t e . Flowers

imperfect; staminate flowers p e d i c e l l a t e , the perianth of 3 imbricate segments, the a n d r o e c i u m of 3 stamens, the stamens alternating with the tepals, the anthers 2- or

4-loculed, dehiscing lengthwise and e x t r o r s e l y , the pollen united into m o n i l i f o r m c h a i n s ; c a r p e l l a t e flowers sessile or s u b s e s s i l e , the perianth of 3 reduced segments, the gy-noecium of 3-5 united carpels, the ovary ellipsoid to ovoid, unilocular, the ovules few to n u m e r o u s , the placentation p a r i e t a l , protruding slightly into the l o c u l e , the styles linear, equal to the c a r p e l s . Fruit ovoid to g l o b o s e , r o s t r a t e , m e m b r a n o u s , opening by decay of p e r i c a r p . Seeds few to n u m e r o u s , globose o r s u b - g l o b o s e .

A genus of 8 species widely distributed in the tropical and subtropical w a t e r s . T h r e e s p e c i e s , H . d e c i p i e n s , H . e n g e l m a n n i i , and H . b a i l l o n i s , occur in the neotropics including B r a z i l . T h e species can be separated by H . d e c i p i e n s being monoecious, with­ out scales partially up the lateral s h o o t , and with pubescent l e a v e s , whereas the other two species a r e d i o e c i o u s , have 2 scales about halfway up the lateral s h o o t , and a r e g l a b r o u s . H a l o p h i l a b a i l l o n i s can be separated from H . e n g e l m a n n i i by the former spe­ cies having distinctly petiolate leaves w h e r e a s the latter species has s u b s e s ­ sile leaves.

H y d r i l l a Rich.

Mém. C l . S c i . M a t h . P h y s . Inst. France 1 2 ( 2 ) : 9, 6 1 , 73 (1814). Type: H y d r i l l a o v a l i f o l i a Rich, nom. i11 eg. ( = H . v e r t i c i l l a t e (L.f.) Royle).

Plants dioecious or m o n o e c i o u s , p e r e n n i a l , g l a b r o u s , submersed, in fresh or brack­ ish waters, propagated by s e e d s , t u r i o n s , or stem f r a g m e n t s . Roots s m o o t h , unbranched, from lower n o d e s . Stems e r e c t , branched or unbranched. leaves whorled, seSsi:le, linear or rarely slightly e l l i p t i c , 1-veined, s e r r a t e , the midrib with dorsal prickles. Inflo­ rescence s o l i t a r y , a x i l l a r y ; spathe of 2 connate b r a c t s , the staminate s u b s e s s i l e , g l o ­ b o s e , dorsiventrally f l a t t e n e d , with subulate appendages and a m i n u t e central k n o b , the c a r p e l l a t e s e s s i l e , t u b u l a r , b i f i d . Flowers imperfect; staminate flowers floating, long p e d i c e l l a t e , the perianth b i s e r i a t e , the sepals 3, ovate to oblong-elliptic, reflexed, strongly c o n v e x e d , the petals 3 , linear to spatulate, narrower than the sepals, spread­ ing to reflexed, the a n d r o e c i u m of 3 stamens, the anthers erect, linear, 4-loculed, laterally d e h i s c e n t , the filament s l e n d e r , s h o r t , the pollen g l o b u l a r , s m o o t h , rather l a r g e ; c a r p e l l a t e flowers s e s s i l e , w i t h a long h y p a n t h i u m , the perianth b i s e r i a t e , the sepals 3, oblong to obovate, convex, the petals 3> spatulate, narrower than the sepals, the gynoecium o f 3 united carpels, the ovary linear, unilocular, the ovules several, o r t h o - to a n a t r o p o u s , the placentation p a r i e t a l , the styles 3 , filiform to subulate,

e n t i r e . Fruits l i n e a r , cylindrical to narrowly c o n i c a l . Seeds c y l i n d r i c a l , g l a b r o u s , 2-6 in one row.

A m o n o t y p i c g e n u s , n a t i v e to t h e Eastern H e m i s p h e r e , that has been introduced into the A m e r i c a s in the last two d e c a d e s . H y d r i l l a v e r t i c i l l a t a has become quite a problem species in many tropical and subtropical r e g i o n s . In f a c t , the species in Florida is known to c o m p l e t e l y c h o k e w a t e r w a y s and is forbidden to be transported by individuals. T h e species t o d a t e is restricted to M e x i c o , Central A m e r i c a , and V e n e z u e ­ la in the n e o t r o p i c s .

L i m n o b i u m Rich.

Mém. C l . S c i . M a t h . P h y s . Inst. France 1 2 ( 2 ) : 66 ( 1 8 1 4 ) . T y p e : L i m n o b i u m b o s c i R i c h . ( = L . spongia (Bosc) Steudel).

H y d r o c h a r e l l a Spruce ex Benth. in Bentham and Hooker, Gen. P I . 3 ( 2 ) : 452 (1883). T y p e : H y d r o c h a r e l l a e c h i n o s p o r a Spruce.

H y d r o m y s t r i a G. Mey., Prim. Fl . Esseq. 152(1818). Type: H y d r o m y s t r i a s t o l o n i f e r a G. M e y e r .

J a l a m b i c e a Cervantes in La H a v e and Lexarza, Nov. Veg. Descr. 2:12 (1825). T y p e : J a l a m b i c e a r e p e n s Cervantes.

R h i z a k e n i a Raf., Autik. Bot. 1 8 8 ( 1 8 4 0 ) . Type: R h i z a k e n i a o v a t a Raf.

T r i a n e a H. Karst., Linnaea 28: 424 (1857). Type: T r i a n e a b o g o t e n s i s H. Karst.

Plants m o n o e c i o u s , p e r e n n i a l , g l a b r o u s , emersed or w i t h stems f l o a t i n g , in fresh w a t e r s , propagated by seeds or s t o l o n s . Roots o n e per n o d e , b r a n c h e d , f i b r o u s , with large root h a i r s . Stems d i m o r p h i c ; shortened stems e r e c t , u n b r a n c h e d , bearing leaves in a r o s e t t e ; e l o n g a t e stems s t o l o n i f e r o u s , b r a n c h i n g . Leaves d i m o r p h i c , the lower s c a l e - l i k e , the u p p e r d i f f e r e n t i a t e d ; scale-like leaves 2 at base of each rosette, m e m b r a n o u s , o v a t e ; differented leaves emergent o r f l o a t i n g , p e t i o l a t e , s t i p u l a t e , lam­

inate, the stipules m e m b r a n o u s , o v a t e , sheathing the developing a p e x , the petiole s t o u t , sometimes inflated, the blade elliptic to c i r c u l a r , the apex o b t u s e to a c u m i ­ n a t e , the base reniform or c o r d a t e , the abaxial surface smooth on emergent leaves or with a e r e n c h y m o u s tissue on floating leaves. Inflorescence imperfect, c y m o s e ; stami­ nate inflorescence sessile or p e d u n c u l a t e , with up to 25 f l o w e r s , w i t h 2 b r a c t s , the bracts o v a t e , the lower shorter than u p p e r ; carpel late inflorescences mostly s e s s i l e , rarely short p e d u n c u l a t e , w i t h 1-6 f l o w e r s , with 1 or 2 separate bracts the bracts o v a t e . Flowers i m p e r f e c t , p e d i c e l l a t e , projected a b o v e the surface of w a t e r ; staminate flowers w i t h e r i n g a f t e r a n t h e s i s , the sepals 3 , narrowly to widely e l l i p t i c , the apex reflexed at a n t h e s i s , g r e e n i s h - w h i t e to y e l l o w i s h , the stamens in 1-6 whorls of 3, inserted on a column of fused filament b a s e s , the anthers 4-loculed, dehiscing lenght-w i s e , the pollen s p h e r i c a l , y e l l o lenght-w , s e p a r a t e ; carpel late flolenght-wers lenght-with pedicels reflexed a f t e r a n t h e s i s , the sepals 3 , narrowly to widely e l l i p t i c , spreading at a n t h e s i s , green­

a n t h e s i s , g r e e n i s h - w h i t e , the staminodia 2 - 6 , in o n e w h o r l , the ovary of 3-9 united c a r p e l s , u n i l o c u l a r , ellipsoid to o b l o n g , the ovules 5 to numerous, the placentation pa­

r i e t a l , the styles equal the c a r p e l s , each split into 2 filiform s t i g m a t a , the stigmata much shorter than the s t y l e , with unicellular p a p i l l a e . Fruit ellipsoid to s p h e r i c a l , b e a k e d , developing in mud o r under w a t e r , the pericarp splitting irregularly. Seeds few to n u m e r o u s , e l l i p s o i d a l , with a short m i c r o p y l a r b e a k , the funiculus p e r s i s t e n t , the testa covered with cylindrical blunt t r i c h o m e s .

A genus of two s p e c i e s ; one s p e c i e s , L i m n o b i u m l a e v i g a t u m , occurs in Amazonia. T h e other s p e c i e s , L . s p o n g i a , is restricted to the eastern United States of America. L i m n o b i u m l a e v i g a t u m occurs in the neotropics from central Mexico to Argentina. Several a u t h o r s , e.g. Dfas-Miranda et a l . (1981) and Hunziker ( 1 9 8 1 , 1 9 8 2 ) , have placed this species in the monotypic genus H y d r o m y s t r i a . Cook and Urmi-Konig (1983), however, dem­ o n s t r a t e the species should be considered within the genus L i m n o b i u m .

O t t e l i a Pers.

Syn. P I . 1: 400 ( 1 8 0 5 ) . T y p e : O t t e l i a a l i s m o i d e s (L.) . Pers.

B e n e d i t a e a Toledo, Arq. Bot. Estado São Paulo 1 ( 4 ) : 81 (1942). Type: B e n e d i t a e a b r a s i l i e n s i s (Planch.) Walpers.

D a m a s o n i u m Schreber, Gen. PI. 1: 242- (1789)· Type: D a m a s o n i u m i n d i c u m Willd., nom. illeg., ( = 0 t t e l i a a l i s m o i d e s (L.) P e r s . ) .

Plants m o n o c l i n o u s or d i o e c i o u s , annual or p e r e n n i a l , g l a b r o u s , submersed or with floating l e a v e s , in fresh w a t e r s , propagated by s e e d s . Roots fibrous. Stems s h o r t , e r e c t , bulb-like axis with greatly condensed internodes. Leaves p e t i o l a t e , petioles terete to 3-5-angled, sheathing at b a s e , often gradually merging into the b l a d e ; blade linear to reniform, entire to crisped on the m a r g i n , the apex rounded to a c u t e , the base cuneate to c o r d a t e , the venation p a r a l l e l , the veins 3 - 1 1 , connected by parallel c r o s s - v e i n s . Inflorescences 1- 3 0 , scapose, pedunculate, with terminal 1-many-flowered s p a t h e ; peduncles e l o n g a t e , projecting the flowers to surface of w a t e r , t e r e t e , to 3-5-a n g l e d ; sp3-5-athes elliptic or ov3-5-ate, with 6 ribs or 2-10 wings, 1-flowered if with perfect or c a r p e l l a t e f l o w e r s , many-flowered if with staminate f l o w e r s . Flowers p e r ­ f e c t or imperfect, the perfect and carpellate sessile, the staminate pedicelled, sepals 3, linear to o v a t e , green w i t h scarious m a r g i n s ; petals 3, oblong to o r b i c u l a r , 2-3 times a s long as s e p a l s , w h i t e , y e l l o w , o r a n g e , p i n k , or b l u e ; s t a m e n s , when p r e s e n t , 3 — 1 5 » the filaments flattened, the anthers linear or oblong, dehiscing lengthwise; c a r p e l s , when p r e s e n t , 6, the o v u l e s n u m e r o u s , the placentation p a r i e t a l , the stigma bifid. Fruits o b l o n g , the apex a t t e n u a t e , the pericarp splitting irregularly. Seeds n u m e r o u s , m i n u t e , oblong or fusiform.

A genus of perhaps 40 s p e c i e s ; one s p e c i e s , O t t e l i a b r a s i l i e n s i s , occurs in the n e o t r o p i c s , being restricted to Minas G e r a i s , the remaning species a r e native to the p a l e o t r o p i c s . O t t e l i a a l i s m o i d e s , however, has become naturalized in the southeastern

United States of A m e r i c a .

Thalassia Banks et Solander ex Koenig

A n n . B o t . 2 : 96 (1805). Type: T h a l a s s i a t e s t u d i n u m K.D. Koenig.

S c h i z o t h e c a E h r e n b . , A b h . K o n g l . A k a d . ' W i s s . Berlin

1 : 4 2 9 ( 1 8 3 4 ) .

T y p e : S c h i z o t h e c a h e m p r i c h i i Ehrenb.

Plants d i o e c i o u s , p e r e n n i a l , g l a b r o u s , entirely submersed, in marine w a t e r s , propagated by seeds or r h i z o m e s . Roots o n e per n o d e , u n b r a n c h e d , from n o d e s . Stems r h i z o m a t o u s , m o n o p o d i a l , scaly, the nodes with short erect shoots bearing 2-6 eligulate l e a v e s , the internodes s h o r t , with fine longitudinal g r o o v e s . Leaves s e s s i l e , linear often s o m e w h a t , f a l c a t e , d i s t i c h o u s , differentiated into green blade and pale basal s h e a t h ; blade e n t i r e , the venation p a r a l l e l , the veins 9 - 1 7 , the apex obtuse. Inflo­ rescence p e d u n c u l a t e , with 1 - 2 flowers in staminate plants and 1 flower in carpellate p l a n t s ; spathes of staminate plant connate on o n e side o n l y , those of carpellate plant connate on both s i d e s . Flowers imperfect, short pedicellate to subsessile; perianth segments 3 , elliptic; staminate flower of 3-12 subsessile stamens, the anthers elongate, e r e c t , 4-locular, dehiscent lengthwise, the pollen spherical, yellow, embedded in gelat­

inous m a t r i x , forming a m o n i l i f o r m chain- later, germinating before reaching the stigma; carpellate flowers of 6-8 carpels, tne ovary muricate, the locules 1 , the ovules few, the placentation p a r i e t a l , the styles equal the c a r p e l s , each split into 2 filiform s t i g m a t a , the stigmata 2 or more times as long as the style. Fruit globose, echinate, b e a k e d , the pericarp splitting irregularly. Seeds f e w , c o n i c a l , thickened b a s a l l y , endosperm of the helobial p a t t e r n , absent in the m a t u r e seed.

A genus o f 2 species; one species, T . t e s t u d i n u m occurs in the neotropics T h a l a s s i a h e m p r i c h i i is restricted to the Indian Ocean and western Pacific Ocean.

T h a l a s s i a t e s t u d i n u m is widely distributed in the Caribbean Sea and Gulf of Mexi­ c o . T h e species forms dense colonies in the sublittoral region from the low water mark to depths of c a . 10 m e t e r s . T h e species can colonize soft s u b s t r a t a , c o r a l , sand dead reef-platform, and rocky s u b s t r a t a . Den Hartog (1970) s t a t e s : " T h a l a s s i a t e s t u d i n u m without doubt is the most important sea-grass along the coasts of the Caribbean and Gulf of M e x i c o " . One of the species most important functions is stabilization and protection of the s u b s t r a t e . T h i s is especially true during hurricanes when wave act ion moves huge amounts of substrate in areas not covered by T h a l a s s i a .

V a l l i s n e r i a Linnaeus

S p . P I . 1 0 1 5 . 1 7 5 3 . Type: V a l l i s n e r i a s p i r a l i s L.

P h y s k i u m Lour., F l . Cochinch. 662 (1790). Type: P h y s k i u m n a t a n s Lour.

Plants d i o e c i o u s , p e r e n n i a l , g l a b r o u s , submersed, in fresh or brackish w a t e r s , propagated by seeds or r h i z o m e s . Roots f i b r o u s , many per n o d e . Stems rhizomatous,

m o n o p o d i a ] , the nodes with short erect shoots bearing 2-6 eligulate leaves. Leaves linear, s t r a p - s h a p e d , finely s e r r u l a t e , 3-zoned, the venation p a r a l l e l , the veins 3-9, the apex o b t u s e . Inflorescences pedunculate; staminate inflorescences with numerous minute flowers enclosed by 2-valved s p a t h e , the peduncles s h o r t , the spathe valves

reflexing at a n t h e s i s ; c a r p e l l a t e inflorescences mostly 1-flowered, rarely few- to many-f l o w e r e d , subtended by a bivalved s p a t h e , the peduncles long, projecting the inmany-flores­ cences to surface of w a t e r , becoming spirally coiled after a n t h e s i s . Flowers imperfect, s e s s i l e ; staminate flowers released by the spathe and floating to surface of w a t e r , the sepals 3, 2 larger, 1 s m a l l e r , e l l i p t i c , g r e e n , the petals 1, rudimentary, the stamens 3, 2 f e r t i l e , 1 s t e r i l e , the fertile often with united f i l a m e n t s , the anthers oblong to g l o b o s e , the pollen s p h e r i c a l , s e p a r a t e ; carpellate flowers p e d i c e l l a t e , the pedicel enclosed in or projecting from s p a t h e , the sepals mostly 3, the petals rudimentary, mostly 3, the staminodia mostly 3, the c a r p e l s mostly 3, the ovary cylindrical, the loc-ules 1, the ovloc-ules n u m e r o u s , the placentation parietal the style 1, the stigma equal the c a r p e l s , b i f i d , the stigmata as long as the s t y l e . Fruit cylindrical to e l l i p s o i d , b e a k e d , the pericarp splitting irregularly. Seeds n u m e r o u s , ellipsoid.

A genus of two s p e c i e s ; one s p e c i e s , V a l l i s n e r i a a m e r i c a n a , occurs in the neotrop­ ics but not in B r a z i l . V a l l i s n e r i a s p i r a l i s is restricted to the Eastern Hemisphere.

V a l l i s n e r i a a m e r i c a n a is most common in North America. However, the species is occasional in the Caribbean Islands, M e s o a m e r i c a , and V e n e z u e l a . Lowden (1982) sep­ arates the species into two v a r i e t i e s , v a r . a m e r i c a n a , which is restricted in the neo­ tropics to M e x i c o , G u a t e m a l a , C u b a , and H o n d u r a s , and v a r . b i w a e n s i s , which i s restrict-ed in the neotropics to the Caribbean Islands and V e n e z u e l a .

J U N C A G I N A C E A E Rich.

R e f e r e n c e s : B u c h e n a u , F. S c h e u z e r i a c e a e . In E n g l . , Pflanzenr. IV 14:1-20 (1906). — H i e r o n y m u s , G. Monografia de L i l a e a s u b u l a t a . Acta Acad. Nac. Sci. Cordova 4:1-52 ( 1 8 8 2 ) . — L a r s e n , Κ. Cytotaxonomical note of L i l a e a . Bot. Not. 119:496-497 (1966).

Plants h e r b a c e o u s , without milky j u i c e , m o n o c l i n o u s , monoecious or d i o e c i o u s , perennials or a n n u a l s , g l a b r o u s , emergent or floating-leaved, of fresh or brackish w a t e r s . Roots fibrous or t u b e r o u s , n u m e r o u s , at the n o d e s . Stems slender to s t o u t ,

r h i z o m a t o u s , the internodes without t e e t h , the tips without turions or t u b e r s . Leaves b a s a l , linear 1-severa 1-veined, flattened to t e r e t e , s e s s i l e , with sheathing b a s e ; sheath a d n a t e to the b l a d e , b i - a u r i c u l a t e , f i b r o u s , often remaining as fibrous cluster after leaves d e c a y , the auricles o b t u s e ; infravaginal scales p r e s e n t , m e m b r a n o u s . In­ florescence either all scapose or both scapose and b a s a l , w i t h o u t a subtending s p a t h e ; scapose inflorescences terminated by spike or spike-like r a c e m e , with all perfect or perfect and imperfect f l o w e r s , then c a r p e l l a t e b e l o w , perfect median, and staminate above, o r possibly c a r p e l l a t e a b s e n t ; basal inflorescence of carpellate flowers o n l y , hidden

amongst the leaf s h e a t h s . Perfect and carpel late flowers h y p o g y n o u s ; perianth mostly p r e s e n t , rarely a b s e n t , the segments 1 or 6., in 1 or 2 series, when in 1 series, then with 1 segment adnate to the anther, when in 2 series, then each series with 3 free s e g m e n t s ; stamens epi-tepalous, 0, 1 , 4 or 6, sessile or subsessile, when 4 or 6 in 2 series of 2 or 3, the anthers 2-loculed, dehiscing by longitudinal slits, the pollen g l o b o s e , s e p a r a t e ; c a r p e l s 0, 1 , 3 , or 6, when 3 or 6 then coherent or weakly connate but separating when m a t u r e , the locules equal to the c a r p e l s , the ovules 1-few per loc-u l e , e r e c t , a n a t r o p o loc-u s , the placentation b a s a l , the styles long and filamentoloc-us with capitate stigmas w h e n carpels 1 , absent with plumose or papillose stigmas when carpels 36. Fruits follicles or angled nutlets, rarely with hooks or horns at apex. Seeds 1 -f e w , t h e e m b r y o s t r a i g h t ; endosperm nuclear in d e v e l o p m e n t , absent in mature seed. Type g e n u s : J u n c a g o Séguier, nom. i11 eg. (=Triglochin L . ) .

A family of four genera and about 15 species. Two genera, Triglochin and L i l a e a , occur in the n e o t r o p i c s .

K e y t o t h e G e n e r a

1 . Inflorescences all scapose spike-like racemes with perfect flowers; carpels 3 or 6 Triglochin 1. Inflorescences both scapose spike-like racemes with perfect and staminate flowers

and basal inflorescences of c a r p e l l a t e f l o w e r s ; carpel 1 L i l a e a

L i l a e a Humboldt ε Bonpland

P I . A e q u i n o c t . 1: 2 2 1 ( 1 8 0 8 ) . Type: L i l a e a subulata Humboldt ε Bonpland (=L. s c l l l o i d e s (Poir.) Hauman).

Plants m o n o e c i o u s , a n n u a l , emersed or f l o a t i n g - l e a v e d , in ephemeral fresh water p o o l s . Roots f i b r o u s , w i t h o u t terminal t u b e r s . S t e m s , s h o r t , slender. Leaves e r e c t , with aerenchyma t i s s u e , the infravaginal scales m e m b r a n o u s . Inflorescence both scapose and b a s a l ; scapose inflorescences with both perfect and staminate f l o w e r s ; basal inflo­ rescences with c a r p e l l a t e flowers o n l y . Perfect flowers with o n e perianth segment, o n e sessile anther a d n a t e to perianth s e g m e n t , and o n e c a r p e l ; staminate flowers with one perianth segment and o n e sessile anther a d n a t e to perianth s e g m e n t ; carpellate flowers w i t h the perianth a b s e n t , o n e c a r p e l , with o n e anatropous o v u l e , the style filiform, to

30 cm long. Fruit a flattened to angular nutlet.

A m o n o t y p i c genus restricted to temperate areas and m o n t a n e tropical marshes from British C o l u m b i a , Canada south to C h i l e and A r g e n t i n a .

T r i g l o c h i n Linnaeaus

S p . p i . 1:338 ( 1 7 5 3 ) ; Gen. PI. 157 ( 1 7 5 4 ) . Type: Triglochin palustre L.

F i g . 6. T r i g l o c h i n striata. A , habit of flowering p l a n t ; B , habit of fruiting p l a n t ; C, enlargement of partially m a t u r e inflorescence w i t h lower portion after loss of anthers following anthesis but b e f o r e fruit m a t u r a t i o n , m i d d l e portion in flower at a n t h e s i s , and upper portion in b u d ; D, flower at anthesis illustrat­ ing the 6 stamens in 2 s e r i e s , 6 perianth segments in 2 s e r i e s , and 3 carpels embedded b e t w e e n the 3-winged r e c e p t a c l e ; E , enlargement of fruiting inflores­ cence illustrating three n u t l e t s b e t w e e n the 3-winged r e c e p t a c l e ; E , n u t l e t . (A, C-D from B o c h e r , et a l . 4 9 7 , C ; B , E-F from Hjerting & Rahn 5 5 6 , C ) .

f i b r o u s , o c c a s i o n a l l y t u b e r o u s . Stems s t o u t , s h o r t . Leaves b a s a l , e r e c t , f e w , t e r e t e , the infravaginal scales m e m b r a n o u s . Inflorescences s c a p o s e , the scapes terminated by 1ong-peduncled spike-like racemes. Flowers perfect; perianth of 6 separate segments in 2 series, similar in texture and color, the segments conchiform; stamens mostly 4 or 6 , s u b s e s s i l e , in 2 series of 2 or 3 ; carpels 3 or 6 , coherent or weakly connate but sep­ arating when m a t u r e , often embedded in angled r e c e p t a c l e , the ovules 1 per locule, the styles a b s e n t , the stigmas plumose or p a p i l l o s e . Fruits angled n u t l e t s .

A cosmopolitan genus of about 12 species represented by two species, T r i g l o c h i n s t r i a t a Ruiz & Pavon and T . p a l u s t r i s L., in the neotropics. The two species can be separated by T . s t r i a t a having nutlets that are semicircular in shape, givingthe entire fruit cluster a spherical a p p e a r a n c e . T h e nutlets of T . p a l u s t r i s , by contrast, are l i n e a r , yielding fruit cluster then is much longer than w i d e .

P O T A M O G E T O N A C E A E Dumortier

R e f e r e n c e s : A s c h e r s o n , P. and P. G r a e b n e r . P o t a m o g e t o n a c e a e . In Engl., Pflanzenr. IV. 11:1-184 ( 1 9 0 7 ) . -- Fernald, M.L. The linear-leaved North American species of P o t a m o g e t o n section A x i l l a r e s . M e m . Gray

Herb.

3 : 1 - 1 8 3 (1932).

- - H a g s t r õ m , J.O. C r i t i ­ cal researches on the P o t a m o g e t o n s . K o n g l . Svenska Vetenskapsakad. H a n d l . V I . 5 5 : 1-281

( 1 9 1 6 ) .

— H a y n e s , R.R. A revision of North American P o t a m o g e t o n subsection P u s i l l i ( P o t a m o g e t o n a c e a e ) . Rhodora 76:564-649 ( 1 9 7 4 ) . -- The Potamogetonaceae in the south­ eastern United S t a t e s . J. Arnold A r b o r . 59:170-191 ( 1 9 7 8 ) . -- Ogden, E.C. The broad-leaved species of P o t a m o g e t o n of North America north of Mexico. Rhodora 4 5 : 5 7 - 1 0 5 , I I 9 - I 6 3 , 171-214 ( 1 9 4 3 ) . — St. John, H. A revision of the North Ameri can species of P o t a m o g e t o n of the section C o l e o p h y l l i . Rhodora 1 8: 1 2 1 - 1 3 8

(1916)

. -- T a y l o r , N . Zan­ ni chel 1 iaceae. N. A m e r . F l . 1 7: 1 3 - 2 7 ( 1 9 0 9 ) . -- Tur, Ν.Μ. Potamogetonaceae, pp. 279¬ 288. In A . L . Cabrera, Flora de la Província de Buenos Aires, Pt. 1 . Coleccion Cienti"-fica del I.N.T.A. Buenos A i r e s ( 1 9 6 8 ) ,

Plants h e r b a c e o u s , without milky j u i c e , m o n o c l i n o u s , perennial or rarely a n n u a l , g l a b r o u s , entirely submersed or with both floating and submersed l e a v e s , in fresh or brackish w a t e r s . Roots f i b r o u s , f e w , a s e p t a t e , at nodes of lower stems. Stems slender, branched or u n b r a n c h e d , often d i m o r p h i c , the lower stems rhizomatous, the upper e r e c t , leafy, e l o n g a t e , the internodes without spinulose t e e t h , the tips often modified into t u r i o n s , without t u b e r s . Leaves a l t e r n a t e or s u b o p p o s i t e , entire to s e r r u l a t e , sessile or p e t i o l a t e , 1-many-veined, stipulate, the stipules forming a tubular sheath around the s t e m , free from or adnate to the base of the b l a d e , the venation p a r a l l e l , c o n n e c t ­ ed by perpendicular c r o s s - v e i n s , the infravaginal scales p r e s e n t , m e m b r a n o u s ; submersed leaves t h i n , linear to o r b i c u l a r ; floating leaves often leathery, lanceolate, to e l ­ liptic or o v a t e . Inflorescence an axillary or terminal spike or panicle of spikes , w i t h ­ out a subtending s p a t h e . Flowers p e r f e c t , h y p o g y n o u s , a c t i n o m o r p h i c ; perianth absent