40 
Larger than the type, stems 2-3 feet in height, leaves some- 
times over 3 inches in length and г line wide, 3-5-nerved. 
Stipules longer and occasionally acute. Spikes 8-12 flowered. 
Mainly distinguished by its large size. This form, which is the 
coarsest in the species, was originally discovered by Prof. Tucker- 
man in the rapids above Niagara Falls, and was considered by him 
a good species, but it seems to me too near foliosus to take 
specific rank. For many years it seemed to have disappeared 
from the original locality until the writer found it in abundance in 
a sluice way between the Falls and the village on the American 
banks. It has recently been collected by Mr. F. V. Coville in the 
United States expedition to Death Valley, California. 
Var. CALIFORNICUS, Morong, Bot. Gaz. x. 254 (1885). 
This form is distinguished by its bushy, vigorous growth and 
large thick stem which is strongly flattened and sometimes winged, 
often % line wide. Many stems, thickly clustered, rise from the 
roots. Leaves not so long or broad as in the preceeding variety, 
but with a dilated mid-rib, reminding one of P. obtusifolius, and 
frequently 5-nerved at the base. Peduncles 4-6 lines long, erect, 
clavate, flattened. Spikes often ripening 12 strongly marked fruit. 
Collected in San Bernardino county, Cal. by the Parish Brothers, 
and by D. Cleveland at San Diego. 
The species has a wide range, occurring in Canada from New 
Brunswick to British Columbia (Macoun); New England to Florida 
and New Mexico and westward to Oregon and California. July- 
September. (Plate XLVII. Two common forms of the fruit are 
figured.) 
24. POTAMOGETON OBTUSIFOLIUS, М. and К. Deut. Fl. i. 855 (182 3). 
P. gramineus, Sowerby, Eng. Bot. iii. t. 2253 (1794), not L. 
P. compressus, Wahl. Fl. Suec. i. p. 107 (1824), not L. 
Stem usually slender, compressed, branching widely, especially 
towards the summit. Leaves linear, 2-3 inches long and 1,-2 
lines wide, obtuse, often mucronate, usually 3-nerved, sometimes 
5- and rarely 7-nerved, biglandular at base, the glands large and 
translucent, the midrib broad and frequently compound. Stipules 
white or scarious, many-nerved, obtuse, 6-9 lines long, often as 
long as or longer than the internodes. Peduncles numerous, %4— 
