237 



long and ^-i 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. terrestris, Raf., and to the submerged 

 form C. linearis, 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. i, 3 (18 14.) 



C. Asagrayi. 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, ^-i mm. long by ^-l', 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. 



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 

 4 mm, 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 



