FRESII-WATER ALG^ OF THE UNITED STATES. 195 



CEdogonia was allowed to dry in a glass, towards tlic close of September, and the 

 greenish residue was placed in water in the following January. By March the 

 resting spores were everywhere in active germination. The first change was a 

 rupture of the two outer coats and the escape, through the slit, of the contents, 

 still surrounded by a very delicate hyaline membrane. By this time the proto- 

 plasm had divided into usually four (sometimes only two or three) greenish masses, 

 each of which was oval in shape and had its own extremely thin, hyaline coat, 

 and was therefore a perfect cell. The old outer shell of the spore laid discarded 

 in the water and soon decayed, and in a little while the hyaline sac surrounding 

 the four daughter-cells itself disappeared, leaving them exposed and naked. After 

 awhile each of these cells opened at one end by means of an annular si)lit, cutting 

 off the apex of the wall and allowing it to lift off like a little lid. Through the 

 circular opening thus made, the contents now emerged. The point of the inner 

 mass was colorless and directed towards the orifice, and the whole moved vigorously 

 backwards and forwards until it finally escaped, as a perfected zoospore. This 

 little bofly simulated very closely the ordinary zoospore, both in appearance and 

 life-history, growing, after a brief period of activity, into an ordinary filament, m 

 precisely the same manner as the zoospores. 



Genus CEDOGONIUM. 



Antheridia et oogonidia in individuo unico. 

 Antheridia and oogonidia in the same individual. 



Remark. — No species of the genus QjJdogonium, as here defined, has as yet 

 been discovered in this country. 



Genus miNGSHEIlMIA. 



Dioica. Antheridia et oogonidia in individuis distinctis orta. 

 Dioecious Antheridia and oogonidia arising in distinct individuals. 



P. ineqiialis, Wood. 



P dioica; cellula basali biloba ; plantis femineis quam plantis masculis perniulto majoribus; 

 oogoniis enormiter globosis vel subovoideis, poro laterale supra medium posito instructis; 

 oosporis forma eadem, sed pauIo minoribus. 



Sijn. — (Edogomum inequale, Wood, Proc. Amer. Philos. Soc, 18G9, p. 141 



Hab. — In stagnis, prope Philadelphia. 



0. dioecious, basal cell bilobate ; female plant very mneh larger than the male plant ; oospo- 

 rangium irregular!}^ globose or subovoidal, opening by a lateral pore above the middle ; 

 resting spores of the same form as the sporangium, but a little smaller. 



Remarks. — This plant seems to be more closely allied to 0. gcmelUparum, 

 Pringsheim, than to any other species. It agrees with it in the inequality of the 

 male and female plants, in the shape of the sporangium, and the position of tlie 

 lateral pore. The diameter of the female plant is often nearly four times that of 

 the male, and the difference in length is much more apparent. The mother-plant is 

 composed of from 3-6 cells in the most distal of which the spermatozoids are formed. 

 I am not able to state how many of these bodies are formed in a single cell, having 



