526 CXXXVI1I. ALISMACE^E. SAGITTARIA. 



ponds in N. H. and Mass. Stem long, branched, almost wholly enclosed in the 

 sheaths. Leaves 2 4' by 2 3", very acute, somewhat crowded. 



9. P. PAUCIFLORUS. Pursh. (P. gramineum. Michx.} Grassy Pond-weed. 

 St. round, dichotomous, filiform ; Ivs. linear, alternate, sessile ; Jls. few in 



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

 to the stipulate base, 23' long, a line wide, 1-veined, of a bright green color. 

 Peduncle an inch long, terminal, bearing 35 greenish fls. above the water, but 

 ripening the seeds below. 



10. P. COMPRESSUS. (P. zosterifolium. Schum.) 



St. compressed, ancipital, flexuous ; Ivs. broad-linear, obtuse ; spike short, 

 peduncle elongated. A very distinct species, in ponds and Fivers. Stem 1 2f 

 long, branching, weak, flattened, green, with sheathing stipules above the nodes. 

 Leaves 3 4' in length, 2" wide, closely sessile, remote, the margins perfectly 

 parallel, ending in an abrupt point. Spadix terminal, i 1' long, on a peduncle 

 1 2/ long, and bearing 525 flowers. Jl. 



11. P. PECTINATUS (and P. marinus. Linn.) Fennel-leaved Pond-weed. 

 St. slender, branched, striate, flexuous ; Ivs. numerous and fascicled in the 



axils, long, narrowly linear, acuminate, on sheathing stipules; spikes cylindrical, 

 the lower fls. remote ; ped. filiform, long. P. lant submersed in deep water, bushy 

 and very leafy, N. Eng. 1 Middle States ! W. to Wis. Lapham ! Leaves 47' by 

 (less than) 1", thin, the midvein scarcely perceptible. Fruit large, purplish, 

 rough, a little compressed, neither carinate, nor umbilicate. Jn. 



12. P. PUSILLUS. Linn. 1 (P. pectinatum. Clark, MS.) Puny Pond-weed. 

 St. filiform, flexuous, branched; Ivs. linear-subulate, membranaceous, very 



acute, sessile, not narrower than the stipules ; sjrikes capitate, few-flowered ; fr. 

 ovoid-compressed, umbilicate each side. Shallow waters, about Cincinnati. 

 Clark! A very delicate- species, wholly submersed. Leaves 1 2' by J", a lit- 

 tle longer than the internodes. Spikes 3 5-flowered, the peduncles \' long. 

 Fruit with distinct pits, as in P. obrutus, and rather inflated. 



(f 



ORDER CXXXVIII. ALISMACEJE. ALISMADS. 



Herbs, aquatic. Lvs. parallel-veined. Fls. racemose or paniculate. 



Fls. perfect or monoecious, regular, not on a spadix. 



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



Sta. definite or indefinite, hypogynous. 



Ova. Carpels several, l -celled and l-seeded. Styles and stigmas several. 



Fr. dry, indehiscent. Seeds straight or curved, destitute of albumen. Genera 5, species 16 7 



Conspectus of the Genera. 



( Flowers all perfect. Stamens 6 Alisma. 1 



( colored, sepals green. ( Flowers nwncecious. Stamens indefinite. . . Sagittaria. 2 



{ \ Anthers thick, short. Leaves cauline. . . . Triglochin. 3 



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



1. ALISMA. 



Celtic alls, water ; the place it inhabits. 



Flowers $ ; stamens 6 ; ovaries and styles numerous, aggregated, 

 becoming in fruit numerous, distinct, compressed achenia. % caules- 

 cent. Lvs. radical. Fls. paniculate. 



A. PLANTAGO. (A. parviflora. PA.) Water Plantain. 

 Lvs. oval, abruptly acuminate or cuspidate, subcordate ; ach. obtusely 3- 

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

 Leaves resembling those of the common plantain, 46' long, f as wide, ending 

 in a short, abrupt point, 7 9-veined, entire, on long, radical petioles. Scape 

 1 2f high. Branches of the panicle verticillate, with bracts at base. Flowers 

 numerous. Petals 3, tinged with purple, roundish, deciduous, larger than the 

 green, ovate, persistent sepals. July. 



/?. parviflora. Torr. Lvs. oval, acuminate, 5 7- veined ; Jls. small. 



2. SAGITTARIA. 



Lat, sagitta, an arrow ; from the peculiar form of the leaf. 



Flowers <? ; c? with about 24 stamens ; 9 with numerous ovaries 



