16 
3. POTAMOGETON AMPLIFOLIUS, Tuckerman, Am. Jour. Sci. and 
Arts, 2d ser. vi. 225 (1848). 
Stems simple, 2-5 feet long, occasionally branching. Floating 
leaves thick, oval or ovate, abruptly pointed at the apex and 
rounded at the base, 2-4 inches long and 114-2 inches broad, 32-40 
nerved, on petioles 3 to 5 inches in length. Submerged leaves 
large, the uppermost often elliptical or oval, 3-6 inches long and 
1-27; inches broad, having about the same number of nerves as 
the floating and sometimes shining; the lowest lanceolate, acute 
at each end, often as much as 8 inches long and 2 inches wide, 
with about 25 nerves. The lowest leaves frequently have the two 
sides of the blade closed and assume a recurved or falcate 
shape. All the submerged leaves are thin and pellucid, and 
are borne on short petioles. Stipules tapering to a long sharp 
point, 2-keeled, closely embracing the stem or spreading with age, 
sometimes 4 inches long. Peduncles thickening upwards, 2 to 8 
inches long. Spikes thick, cylindrical, 1 to 2 inches long. Fruit, 
2 to 2% lines in length by 1 ¥ lines in breadth, with a thick, hard 
shell, turgid, obliquely obovate in shape, 3-keeled, the middle keel 
prominent; sides not impressed, face more or less angled; style, 
sub-apical; embryo slightly incurved. In the Western lakes and 
ponds the plants with the large oval or ovate submerged leaves 
are most common, and those with recurved leaves rare, while the 
reverse is the case in Eastern waters. Aberrant forms occur with 
petioles very slender and 10 or more inches in length. I have 
also collected occasional specimens which have at the lowest part 
of the stem small, opaque, oblong, long-petioled leaves similar to 
those found on P. pulcher; and, also, a very rare form which re- 
sembles Р. natans in its upper foliage and in fruit, except the em- 
bryo. Canada from Ontario to Vancouver's Island (Macoun). 
United States from New England to Kentucky, and westward to 
Minnesota and Nebraska. An endemic species. July to Sept. 
(Plate XXVII, showing below one of the curved submerged 
leaves.) 
4. POTAMOGETON PULCHER, Tuckerm. Am. Jour. Sci. and Arts, Ist 
ser. xlv. 38 (1843 
Stems simple, terete, black-spotted, from 1 to 2 feet high. 
Floating leaves usually massed at the top on short, lateral branches, 
