ALISMACE^E. S70 



4. P. perfolia'tum. 



Leaves cordate, clasping the stem, uniform, all immersed ; spikes terminal ; 

 flowers alternate. A common species, growing in ponds and slow waters, 

 wholly below the surface except the purplish flowers. Stem dichotomous, 

 very leafy, 6—10 inches long. Leaves alternate, apparently perfoliate near 

 the base, 1-^ inch long, i as wide, obtuse, pellucid. iSpadix on a short pedun- 

 cle (1—2 inches), few-tiowered. Ji. Perfoliate Pond-weed. 



5. P. PAUCI'FLORUM. P. P. gramineum. Jtfz. 



Stem round, dichotomous, filiform ; leaves linear, alternate, sessile ; fowera 

 few in a spadix. A delicate species, in rivers, &c. Leaves numerous, obtuse 

 tapering to the stipulate base, 2— 3 inches long, a line wide, 1-nerved, of a 

 bright green color. Peduncle an inch long, terminal, bearing 3—5 greenish 

 fls. above the water, but ripening the seeds below. Grass-leuvcd Pond-ioeed. 



6. P. pectina'tum. 



Leaves setaceous, parallel, approximate, in 2 rows ; flowers Tew in a spike, 

 scattered. The whole plant immersed in water except the spikes, which are 

 terminal, composed of a few, remote, green flowers. Leaves very numerous, 

 alternate, pointed, 1-ribbed, so arranged on 2 opposite sides of the stem as to 

 give it a pectinate appearance. Jl. Femiel-lcavcd Pond-weed. 



7. P. COMFR'eSSUM. Torr. P. zosterifolium. Sc/mm.? 

 Stem compressed, ancipital, flexuous; leaves broad-linear, obtuse; spike 



short, peduncle elongated. A very distinct species, in ponds and rivers. Stem 

 1 — 2 feet long, branching, weak, flattened, green, with sheathing stipules 

 above the nodes. Leaves J — 4 inches in length, 2 lines wide, closely sessile, 

 remote, the margins perfectly parallel, ending in an abrupt point. Spadix 

 terminal, 4 — 1 inch long, on a peduncle 1 — 2 inches long, and bearing 5 — 25 

 flowers. July. Grassy Potamogeton. 



ORDER CXL. ALISMACEtE. The Water Plantain Tribe. 



Fls. — Perfect or monoscious, regular, not on a spadix. 



Perianth. — Cal. 3-sepaIed, green. Cor. 3-petaled, colored (green in the suborder). 

 Sta. — Definite or indefinite, hypogynous. 



Ova. — Carpels several, 1-celled and 1-seeded. Styles and ii/g^was several. 

 Pr. — Dry, iiideliiscent. Seerfj straight or curved, destitute of albumen. 

 Aquatic herbs. Leaves parallel-veined. Flowers racemose or paniculate. 

 Conspectus of the Genera. 



I Flowers all perfect. Stamens 6. . . Alisma. 1 



f colored, sepals green. ( Flowers monoscious. Stamens indefinite. Sagitiaria. 2 



) ( Anthers thick, short. Leaves cauline. Triglochin. 3 



Petals ( green, like the calyx. \ Anthers linear. Leaves all radical. . Scheuchzeria. 4 



1. A LI'S MA. 



F'lowers perfect ; stamens 6; ovaries and styles numerous, 

 aggregated, becoming in fruit numerous, distinct, compressed 

 achenia. 



Celtic alis, water ; the place it inhabits. Perennial, caulescent. Leaves 

 radical. Flowers paniculate. Sepals while. 



A. planta'go. 



Leaves oval, abruptly acuminate or cuspidate, subcordate ; achenia obtusely 

 3-cornered. A common, smooth, handsome inhabitant of ponds and ditches. 



