On the Affinities of Ceratophyllacea. 49 



The two species of Ceratophyllum admitted by Linnaeus, 

 were distinguished chiefly by the presence or absence of lateral 

 *pines. In a recent revision of the genus by Chamisso,* six 

 species are described, and a seventh is indicated by Dr. Wal- 

 lich. If these be distinct species, as is most probable, there 

 are doubtless others to be discovered. In this country, spe- 

 cimens are rarely to be met with in fruit, and consequently the 

 genus is little known. I am indebted to Dr. Torrey for the op- 

 portunity of examining specimens with ripe fruit, collected by 

 him, several years since, near Princeton, New Jersey, which 

 are wholly different from any species described or figured by 

 Chamisso. They agree, however, with a specimen from Su- 

 rinam, communicated by the late Mr. Schweinitz, except that 

 the fruit is a little larger. This plant, which I am disposed to 

 consider an undescribed species, resembles C. muricatum of 

 Chamisso more than any other, from which it differs not only 

 in the shorter and more slender terminal, and two lateral spines 

 of the fruit, but also more particularly in the whole margin 

 being beset with slender spines. It may therefore be called C. 

 echinatum. 



In descriptions of a seed, it is important that the relation 

 of the hilum to the chalaza and micropyle should be especially 

 noticed ; or, which amounts to the same thing, that the spcrmic, 



tremity opposite the chalaza or organic base, which, as in all anatropous 

 seeds, occupies the geometrical apex of the seed. The radicle is ap- 

 proximated to the hilum in the former case, but points in (he opposite 

 direction in the latter. See a figure given by Dutrochet, in Mem. du 

 Museum, 8, t. I, in which the embryo is plainly represented as dicotyle- 

 donous, although the author, adopting a very absurd view, attempts to 

 prove it to be monocotyledonous. See also, especially, the admirable 

 plate in the Memoir of Ad. Brongniart,* illustrative of the mode of im- 

 pregnation, and the structure of the ovule and seed, in Nuphar lutea, 

 which incontestably demonstrates the correctness of the view of Brown 

 and others respecting the nature of the sac which encloses the embryo. 



* Ann. Sci. Nalurellts, 12, (. 39. 



* Linnaa 4, p. 503. 



VOL. IV. 7 



