674 OEDEa 134.— NAIADACBiE. 



and submersed, only the flowers arising above the surface of the water. 

 Spadix (or spike) pedunculate, 3 — 10-flowered. Lvs. stipulate, par- 

 allel-veined, lower alternate, the upper mostly opposite. Fls. small, 

 greenish. 



$ Leaves of two kinds ; tbo floftting, oval-elllptical, coi-laceous pctlolnte, stipules free 

 from tho petiole, coimate; submersed leaves thin, (*) 



* Floating leaves broader than the submersed ones, (a) 



a Leaves all conspicuously stipulate Nos. 1, S 



a Leaves (the submersed ones) almost destitute 'jfatipiiles Nos. 8, 4 



• Floating leaves smaller than the ample submersed ones No. G 



$ Leaves of one kind only, all growing beneath tlie water's Burlace. (*) 



• i^ipules entirely free from tlm petiole or leaf, (a) 



a Leaves lanceolate, potiolate or merely sessile Nos. 6, 7 



a Leaves oval or obiong, broad and clasping at base Nos. 8, 9 



a Leaves linear, — Stems evidently compressed more or less Nos. 10, IT 



— Stems terete, very slender Nos. 13, 18 



* Stipules united with the sheathing base of the leaf. Nos. 14, 16 



1 P. natans Ia Broad-leaved Pond-weed. Floating lvs. coriaceous, oblong, 

 or elliptic-ovate, acute or obtuse or cordate at base, on long petioles, submersed 

 ones linear-lanceolate, membranous, clong.ited, attenuated to petioles at base, 

 lowest reduced to mere petioles ; stipules connate, distinct froni the petiole, 

 elongated ; spikes rather dense, shorter than the peduncles ; fruit somewhat 

 semi-globous, roughish, more or less carinate at tho baclc. — A very common 

 species, in slow waters or ponds, IT. Bng. to "Wis. St. slender, 1 to 3f long, ac- 

 cording to the depth of tho water, branched. Upper lvs. 2 to 4' long, aboai 

 half as wide ; petioles 2 to 8', submereed. Spike 1 to 2' long. Jl., Aug. 



2 P. heteroph^llus Schreb. Floating lvs. lanceolate or oblong, 5 to t-veined. 

 tapering to the petioles, scarcely coriaceous, submersed lvs. long^ narrowly linear, 

 membranous, acute, 1-veined, slightly tapering to the sessile base ; stip. nearly 

 distinct, resembling the lvs. ; spikes dense, on thickened peduncles ; fr. com- 

 pressed, Buborbioular. — Ponds and slow waters, frequent. St. round, slender or 

 filiform, often branched. Lower lvs. 3 to 6' by 1^", rei»ot«, upper about 2 to '■¥ 

 by J'. Spikes 1' long, peduncles 2 to 4'. (P. Claytonia Tuekerman.) 



3 P. diversifoUua Bart. St. fihform, branching ; upper lvs. oval or lance-oval, 

 5-veined, on short petioles, lower ones submerged, sessile, filiform, alternate, often 

 densely fascicled, not at all reticulated, obtuse. — Common in pools and ditches 

 A very slender and delicate species, only the upper lvs. arising to tho surface. 

 These are G to 10" by 2 to 4", acute at each end, on hair-like petioles 3 to 6" long. 

 Spadices dense, short, 5 to 6-flowered. Jl. (P. setaceum Pli.) — ^Varies with tho 

 leaves nearly all of either kind. 



4 P. h^bridus Mx. Floating lvs. eUiptic-oblong, coriaceou.s, scarcely veined, 

 longer than their petioles ; submersed lvs. long-linear, thin, sessile ; stipules above 

 equaling the petioles, those of the submersed lvs. very short or wanting ; spikes 

 cylindric, dcn^c, on short, thickened pod. ; fruit keeled on the back, seed coiled 

 kito a ring. — Pools and slow waters, S. ? and "W". States. Sts. mostly simple, very 

 slender, 1 to 3f long. Lower lvs. 3 to 5' long, alternate, upper opposite, 1' to 18". 

 Spike about 1'. A handsome species. 



5 P. fliiitans Roth. Floating lvs. opposite, oval-lanceolate, coriaceous, acute at 

 each end, shorter than the petioles ; submersed lvs. larger than the floating, lan- 

 ceolate, sessile, short-acuminate, strongly veined, wavy, thin, not shining, faintly 

 reticulated; stip. large, connate; ped. thickened, cylindric. — In clear, deep 

 waters, N. New Eng. and Can. Sta. simple or branched, several feet long. Sub- 

 mei-sed lvs. 5 to T long, a third as wide, the floating 2 to 3' long. Stip. 2 to 3' 

 long. Spikes 2' long, rather dense-flowored. Aug. 



G P. Mcens L. Lvs. shining, oblong-lanceolate, acuminate, flat, large, tho short 

 petioles continuing in a thick midveiu ; spikes long, cylindric, many-flowered ; 

 ped. thickened upward ; fr. slightly keeled.— y Can., N. Eng., &c. Rivera and 

 lakes. Distinguished for its large leaves which are very pellucid, and, when dry, 

 shining above, conspicuously cross-veined, 3 to 6' long, an inch or more wide, 

 each with a lanceolate, double stipule above its base. Spadix 2' long, of nu- 

 merous green flowers, on a peduude 2 or 3 times as long, tliick and enlarged iij>- 

 wai^s. Jn. 



