60 DESMins OF THE UNITED STATES. 



Thi? i^ one of the Uirgest ^peoies of the genus and most 

 common. The end view is nearly a perfect circle ; front view 

 of a semi-cell constitutes about two-thirds of a circle ; a dis- 

 tinct border is always present, and often appears striated. 



Tar. MINOE, Xord. Plate XT, lig. 10. Plate LX. tig. 18. 



This form is in all essential points like the last, except iu 

 dimensions. 



I have found almost every possible variety of size, measur- 

 ing in diameter from 'lO to -tO u. This fact furnishes a pre- 

 sumptive evidence that the smaller forms are merely unde- 

 veloped conditions ; young plants evolved from sporangiums, 

 in accordance with Hofmeister's theory. See Ixteoductiox, 

 p. 19. 



(.'. PSErroooxxATi'S, Xord. Plate XV, fig. 11. Plate LX, figs. 

 10, 11. 

 Similar to the two preceding in form and structure, bat iu 

 size tisually smaller than the typical plant. The distinctive 

 feature is iu the arrangement of the chlorophyl ; this is not 

 homogeneous, but divided in each semi-cell, iu front view, 

 into two parts, and in end view, into four parts. 



Marsh pools, Pennsylvania. 



The value of the arrangement of the chlorophyl as a spe- 

 ciflc character, needs, I think, further corroborative evidence. 



C. Clevei, ^Lund. '. Wolle. (Feniiim Clevfi. Lund.) Plate LXI. 

 fig. 27. 

 Cell snbcylindrical, 2 J -.3 times longer than broad, some- 

 what constricted in the middle : semi-cells cylindric-sttb- 

 couical, ends distinctly attentiated and rounded at apices : 

 vertical view a perfect circle. Xuclei large, elliptic single 

 or rarely twiuued. Membrane finely punctate, at apices 

 subgrauulate punctate. 



Diameter 40-50 /.i. Length lln-lis /.t. 

 Brown's Mills, New Jersey. 



The plant is slightly larger than Lundell's form, but so 

 good a counterpart in form and structure, I take it to be the 

 same species ; by measurement the constriction is somew hat 

 deeper. The decided constriction makes the natural position 

 of this form, I think, a member of the present genus, not- 

 withstanding the observations made by Lundell iu the 

 arrangement of the chlorophyl. 



0. Ti-nvAiTEsii. Ealfs. Plate XY, fig. 19. Phite LXI, fig. 2S. 

 Cells two or three times longer than broad, fusiform in 

 front view ; circular iu end view ; constriction a shallow 



