674 Ordbb 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. 



S Leaves of two kinds ; the floating, oval-elliptical, coriaceous petiolate, stipules freo 

 from the petiole, connate ; submersed leaves thin, (*) 



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



a Leaves all conspicuously stipulate Nos. 1, 2 



a Leaves (the submersed ones) almost destitute uf stipules Nos. 8, 4 



* Floating leaves smaller than the ample submersed ones No. 6 



§ Leaves of one kind only, all growing beneath the water's surface. (*) 



• Stipules entirely free from the petiole or leaf, (a) 



a Leaves lanceolate, petiolate or merely sessile Nos. 6, T 



a Leaves oval or oblong, broad and clasping at base N0S..8, 9 



a Leaves linear, — Stems evidently compressed more or less .Nos. 10, 11 



. — Stems terete, very slender. Nos. 13, 18 



• Stipules united with the sheathing base of the leaf. , . .Nos. 14, 15 



1 P. natans L. Bboau-lbavbd Pond-weed. Floating Iva. coriaceous, oblong, 

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

 ones linear-lanceolate, membranous, elongated, attenuated to petioles' at base, 

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

 elongated ; spikes rather dense, shorter than the peduncles ; fi:uit somewhat 

 semi-globous, roughish, more or less carinate at the baclA — ^A very common 

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

 cording to the depth of the water, branched. Upper lvs. 2 to i' long, about 

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



2 P. heteroph^Uus Schreb. Pleating lvs. lanceolate or oblong, 5 to 7-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, suborbioular. — Ponds and slow waters, frequent. St. round, slender or 

 filiform, often branched. Lower lvs. 3 to 6' by IJ", remote, upper about 2 to 3' 

 by J'.. Spikes 1' long, peduncles 2 to i'. (P. Claytonia Tuckerman.) 



.3 P. diveraifolius Bart. St. filiform, branching; upper lvs. oval or lance-oval, 

 5-veinBd, 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 the surface. 

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

 Spadices dense, short, 5 to 6-flowored. Jl. (P. setaceum Ph.) — Taries with the 

 leaves nearly aU of either kind. 



4 P. h^bridus Mx. Floating lvs. elliptic-oblong, coriaceous, scarcely veined, 

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

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

 cylindrio, dense, on short, thickened ped. ; fruit keeled on the back, seed coiled 

 into 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, V to 18". 

 Spike about 1'. A handsome species. 



5 P. flCiitaus 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-aouminate, strongly veined, wavy, thin, not shining, feintly 

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

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

 mersed lvs. 5 to 7' long, a third as wide, the floating 2 to 3' long. Stip. 2 to 3' 

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



'Q P. iTicens L. Lvs. shining, oblong-lanceolate, acuminate, flat, large, the shbrt 

 petioles continuing in a thick midvein; spikes long, cylindrio^ many-flowered; 

 ped. thickened upward ; fr. shghtly keeled.— 2i Caa, N. JEng., &c. Rivers and 

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

 sliining above, conspicuously cross-veined, 3 to 5' 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 peduncle 2 or 3 times as long, thick and enlarged up- 

 wards. Jn, 



