436 ALISMACE^. (WATER-PLANTAIN FAMILY.) 



at the base (l'-4' long, the petiole 4' -12' long); stipules not winged nor 

 ridi/ed; peduncle not thickened; fruit obtuse on the back when fresh. (P. lonchites, 

 Tucker m.) P. oblongus, Viv., is a small-fruited form. Ponds and slow 

 streams; common. (Eu.) 



12. P. lictcropliyllllS, Schreber. Stem slender, branching; immersed 

 leaves lanceolate or linear and sessile, or only the upper petioled ; floating leaves 

 elliptical, varying to oblong-linear, thinnish (l'-2' long), on filiform petioles ; 

 united stipules %-ribbcd on the back; peduncle ojl.cn thickened upwards; fruit slfi/lttli/ 

 keeled when dry (one half smaller than in the preceding). (P. gramineus, L. 

 in part, Fries, -c. P. Claytonii, Tuckerm.) In shallow pools and ditches, as 

 well as streams; common. (Eu.) 



P. cufsFUS, L., I have not seen in this country. Mr. Tuckerman informs 

 me that he has seen a specimen in a European herbarium, purporting to have 

 been gathered in Delaware. If found, it may be distinguished from No. 8 by 

 its lanceolate and wavy-crisped 3-nervcd leaves. See Addend. 



P. DENS us was admitted into the first edition on the authority of Beck from 

 Schweinitz. I apprehend some mistake about it. The species, if in the coun- 

 try, may be known by its leaves being all opposite and without stipules. 



ORDER 116. AL.ISMACEJE. (WATER-PLANTAIN FAMILY.) 



Marsh herbs, mth scape-like flowering stems, and perfect or monoecious 

 flwvers, not on a spadix, furnished with both calyx and corolla : sepals and 

 petals each 3, distinct. Ovaries 3 -many, distinct or partly so, or if united 

 separating at maturity, forming as many 1 - 2-seeded pods or achenia. Seed 

 ascending or erect. Embryo without albumen. Stamens hypogynous, 6 

 to many : anthers extrorse, 2-celled. Leaves sheathing at the base. Com- 

 prises two very distinct suborders, viz. : 



SUBORDER I. JUNCAGINE^E. THE ARROW-GRASS FAMILY. 



Calyx and corolla colored alike (greenish). Seed anatropous, with a 

 straight embryo. Leaves petiole-like, without a blade. 



1. TRIGLOCIIIN. Flowers perfect. Ovaries 8-6, united into one, but separating in fruit. 



2. SCIIEUCIIZERIA. Flowers perfect. Ovaries 3, nearly distinct, forming diverging pods In 



fruit. 



SUBORDER II. ALISMEJE. THE WATER-PLANTAIN FAMILY. 



Calyx green and persistent. Corolla white, deciduous. Seed cainpy- 

 lotropous: embryo bent double or hook-shaped. Loaves commonly fur- 

 nished with a blade. 



8. ALTSMA. Flowers perfect, with definite, mostly 6 stamens. Carpels numerous, whorled. 



4. ECIIINODOHUS. Flowers perfect, with 7-21 stamens. Carpels capitate, ribbed. 



5. SAG ITT ARIA. Flowers monoecious. Stamens indefinite. Carpels capitate, winged. 



