352 ALISMACEJE. 



small pointed ; peduncles thickened upwards; tpiles cylindrical, many flowertd; 

 nutlets slightly keeled. 



Ponds and deep stream:;. June. Stem long, branched. Leaves large, very pel- 

 lucid, and when dry shining above, beautifully veined. 3 to 6 inches long. Yi to * 

 inch wide, acuminate, each with a lanceolate bract above the base. Spike 2 inches 

 long, of numerous green flowers. 



6. P. PERFOLIATUS, L. Perfoliate Pondweed. 



Leaves clasping by a heart-shaped base, ovate or ovate-lanceolate, sometimes 

 round ovate, obtuse ; spikes terminal, with a few alternate flowers; nutlets rounded 

 on the back, short-pointed. 



Ponds and rivers, common. July. Stem 2-forkcd, very leafy, 6 to 10 inches 

 long. Leaves shining, 1 to \]/ z inch long, \6 as wide, obtuse, flat, more or less 

 wavy or crisped. Spike on a peduncle, 1 to 2 inches long. 



7. P. pauciflorus, Pursh. Grass?/ Pondweed. 



Stem very slender, and filiform, flattish; leaves narrowly linear, acutish; spi7.es 

 few-flowered, short-peduncled ; nutlets obliquely lenticular, distinctly crested on 

 the back. 



Ponds and streams, common. July, Aug. Leaves numerous 2 to 4 inches long, 

 scarcely 1 line wide, obscurely 3-nerved, of a bright green color. Flowers 3 to 5, 

 greenish, on a terminal peduncle an inch long. 



8. P. pectinatus, L. Fennel-leaved Pondweed. 



Stems thread-like, many-times forked; haves bristle-form, 1-nerved; spikes inter- 

 rupted, on long peduncles ; nutlets rounded-obovate. 



Ponds and deep streams. June. Plant much branched and leafy. Leaves 3 to 

 f> inches long, less than 1 line wide, thickish. Spike in clusters of 3 or 4 seperated 

 in fruit by considerable intervals. Fruit purplish. 



* * * Stipules none,; leaves all opposite and immersed. 



9. P. DFNSUS, L. Dense Pondweed. 



Leaves pellucid, elliptical or lanceolate, clasping ; spike few-flowered, short-pe- 

 duncled, reflexed in fruit; nutlets beaked and keeled. Bethlehem, Schwenitz. 



Order 115. ALISMACEIE.— Water-Plantain Family. 



Marshy herbs, with parallel-veined leaves sheathing at the base, scape-lil;e flowering 

 Stems, and perfect or monoecious flowers, not on a spadix, furnished with both calyx 

 and corolla; sepals and petals each 3, distinct. Stamens definite or indefinite. Ova- 

 ries 3 to-many, distinct or partly so. Styles and stigmas as many as the ovaries. 

 Fruit dry, indehiscent, 1 to 2-seeded. 



Sub-order i. JUNCAGINEiE. Arrow-Grass Family. 



Calyx and corolla colored alike (gjeenish). Seed ana- 

 tropous, with a straight embryo. — Leaves petiole-like without 

 a blade. 



1. TRIGLOCHIN, Linn. Arrow-Grass. 



Or. treis, three, and ghchin, a point; ia allusion to the points of the caprol*. 



Sepals and petals nearly alike, ovate, concave, deciduous. 



