674 Order 134— NAIADACEJS. 



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. 



§ Loaves of two kinds ; the flouting, 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 Nob, 1, 8 



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



* Floating leaves smaller than the ample submersed ones... No. 5 



5 Leaves of one kind only, all growing beneath the wuter's surface. (•) 



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



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



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



a Loaves linear, — Stems evidently compressed mora or less Nos. 10, 11 



— Stems terete, very slender Nos. 12, IS 



* Stipules united with tho sheathing base of the leaf Nos. 14, 11 



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

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

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

 lowest reduced to more petioles ; stipules connate, distinct from tho petiole, 

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

 somi-globous, roughish, more or less carinate at the back. — A very common 

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

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

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



2 P. heteroplry"llus Schreb. Floating lvs. lanceolate or oblong, 5 to 7 -veined, 

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

 membranous, acute, 1-veincd, slightly tapering to tho sessile base ; stip. nearly 

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

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

 filiform, often branched. Lower lvs. 3 to 6' by \\", remoto, upper about 2 to & 

 by &'. Spikes 1' long, peduncles 2 to 4'. (P. Claytonia Tuckerman.) 



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

 5-veinod, 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 G" long. 

 Spadices denso, short, 5 to G-fiowered. Jl. (P. setaceum Ph.) — Varies with the 

 leaves nearly all of cither kind. 



4 P. hybridus Mx. Floating lvs. elliptic-oblong, coriaceous, scarcely veined, 

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

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

 cylindric, dense, on short, thickened ped. ; fruit keeled on tho 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, 1 to 18". 

 Spike about 1'. A haudsoine species. 



5 P. fluitans Roth. Floating lvs. opposite, oval-lanceolate, coriaceous, ncute 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. Now Eng. and Can. SU. simple or branched, several feet long. Sub- 

 mersed lvs. 5 to 1' long, a third aa wide, the floating 2 to 3' long. Stip. 2 to 3' 

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



6 P. luceus L. Lvs. shining, oblong-lanceolate, acuminate, flat, large, the short 

 petioles continuing in a thick mid vein ; spikes long, cylindric, many-fiowered ; 

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

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

 Bhining 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 onlarged tip- 

 wards. Jn. 



