PoTAMOGETON. CXXXVII. NAIADACEZ. 525 
1—3f long according to the depth of the water, branched. Upper leaves 2—4’ 
by 8—16”, petioles 2—8’, submersed about 4 as wide. Spike 1—2/ long, 
20—40-flowered. Jl. Aug.—Varies with the lower leaves all reduced to peti- 
oles. In the Wisconsin plant the leaves are all subcordate, fruit acutely cari- 
nate but not lunate. 
2. P. Cuayronu. Tuckerman. (P. fluitans? Ph., Bw., Torr., §c.) 
Floating ; /vs. lanceolate or oblong, tapering to long petioles (sometimes 
on short petioles, E. T.), scarcely coriaceous, submersed leaves long, narrowly 
linear, membranaceous, acute, l-veined, slightly tapering to the sessile base; 
spikes rather loose, on long peduncles; fr. compressed, suborbicular.—Ponds and 
slow waters, frequent. Stems round, slender or filiform, often branched. Lower 
leaves 3—6’ by 14’, remote, upper about 2—3’ by 3’. Spikes 1’ long, pedun- 
cles 2—4’ 
“B1 (P. heterophyllus. Torr.) Lower lws. approximate, lowest slightly petio- 
late ; ped. shorter—Uxbridge, Mass., Rickard! Probably common. A beauti- 
ful variety. Fruit not seen. 
3. P. piversiFo.ius. Bart. (P.setaceum. Ph.) Setaceous-leaved Pond-weed. 
Upper lvs. lanceolate, opposite, 5-veined, on short petioles, lower ones sub- 
merged, sessile, filiform, alternate, dense, axillary—Common in pools and 
‘ ditches. A very slender and delicate species, only the upper leaves arising to 
the surface. These are 6—10” by 2—4”, acute at each end, on hair-like peti- 
oles 5—6"' long. Spadices dense, short, 5—6 flowered. July. 
@. Submersed leaves few, not fascicled in the axils. 
§ 2. Leaves all submersed, uniform. 
4. P. tucens. Shining Pond-weed. 
Tvs. lanceolate, flat, large, the short petioles continuing in a thick mid- 
vein; spzkes long, cylindric, many-flowered.—2| Can., N. Eng., &c. Rivers and 
lakes. Distinguished for its large leaves which are very pellucid, and, when 
dry, shining above, beautifully veined, 3—5’ long, acuminate, 3—1’ wide, each 
with a lanceolate bract above its base. Spadix 2’ long, of numerous, green 
flowers, on a peduncle 2 or 3 times as long, thick and enlarged upwards. June. 
5. P. oprotus. Wood. Lyndon Pond-weed. 
Lvs. glossy, linear-lanceolate, sessile, rather acute, only the midvein con- 
spicuous, alternate, approximate, the lower stipules wanting; spikes long-pedun- 
culate; achenia inflated, subhemispherical, margined on the back, beak incurved 
both sides, conspicuously umbilicate——Passumpsic river, Lyndon, Vt.! A 
remarkable species, differing widely from any other with which I am acquainted. 
Stem round, slender, simple. Leaves uniform, 3—4’ by 2’, tapering to the 
slightly clasping base, the two upper opposite. Spike dense, 14/ long, peduncle 
3’ in length. Fruit with 2 little pits. 
6. P. preLoncus. Wolff. Long-stalked Pond-weed. 
Lvs. oblong or ovate, obtuse, many-veined, with 3 stronger veins, all reticu- 
lately connected, base amplexicaul; ped. very long; spike cylindrical, many- 
flowered; fr. ventricose, lunate, acutely carinate on the back—Ponds and 
rivers, Northern States and Can. The plant is wholly submersed, sending up 
its spike to the surface on a very long stalk. I have gathered it in Niagara 
river, growing in depths of 6 or 8f. July, Aug. 
7. P. perFouiAtus. Perfoliate ur Clasping Pond-weed. 
Lvs. cordate, clasping the stem, uniform, allimmersed; syrkes terminal; fs. 
alternate.—A common species growing in ponds and slow waters, wholly below 
the surface except the purplish flowers. Stem dichotomous, very leafy, 6—10/ 
Jong. Leaves alternate, apparently perfoliate near the base, 13’ long, 4 as wide, 
obtuse, pellucid. Spadix on a short peduncle (1—2’), few flowered. Jl. 
8. P. Ropginsu. Oakes. Robbins’ Pond-weed. . 
Tvs. lance-linear, approximate, sheathing the stem with the adnate stipules, 
lamina auriculate at base, margin minutely ciliate-serrulate; spikes oblong, 
small and few-flowered; ped. shorter than the leaves.—First discovered by Dr. 
Robbins! in Pondicherry Pond, Jefferson, N. H. Since found in many other 
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