237 
long and 34-1 mm. broad, flat on the face, mostly with a small 
apical notch and narrow apical wings, the grooves between the 
lobes deep. The fruit often varies from oblong to obovate, thus 
approaching the character of the following species. 
. To the terrestrial form of this species have been referred C. 
brevifolia, Pursh., and C. ¢errestris, Raf., and to the submerged 
form C. /inearis, Pursh., but no one can tell without an examina- 
tion of their specimens whether these authors had this or the fol- 
lowing species in mind. 
A wide-spread species, but most common in Northern waters. 
It occurs throughout the Dominion of Canada, and in nearly all 
parts of the United States. Found also in South America, 
Europe and Asia. 
7. C. heterophylla. Pursh. Fl. Am. 1, 3 (1814.) 
C. Asagrayt. Hegelm. Monog. p. 54 (1864.) 
Very similar to No. 6 in general appearance, foliage and 
habits; like that it has terrestrial, submerged and intermediate 
forms. Fruit smaller, 3-1 mm. long by /-1; mm. broad, generally 
obovate, with a deep, broad notch at the apex, thick, almost 
ventricose near the base, lobes obtusely angled, with a small groove 
between them, wingless or with a narrow wing or raised border 
on the upper margin; stigmas usually longer than the fruit, erect, 
more or less persistent. 
Frequently confounded with C. verna. After examining 
many private collections, and finding fault with the collectors for 
badly mixing up the two species, I was somewhat taken aback, 
as well as much amused, upon re-examining my own specimens 
collected some years since, to find that nearly all which I had 
marked C. verna were C. heterophylla. 3 
This species is more common than the foregoing in Southern 
waters, but it occurs in Canada, and ranges from New England to 
Florida and Louisiana, and west to Missouri and Colorado. 
8. C. stenocarpa. Hegelm. Verhand. Bot. Brand 10, 114 (1868 ?). 
Floating leaves 10-12 mm. long, obovate, rounded and entire 
at the apex, three-nerved, the blade 8-10 mm. long and about 
4mm. broad, tapering into a short, margined petiole, marked 
with stellate scales. Submerged leaves linear. Styles erect, 
twice as long as the fruit, deciduous. Fruit flat, with a well 
