THE GREEN ALGAE OF NORTH AMERICA 55 



successive division, ovoid, with 2 cilia, escaping in a gelatinous 

 vesicle by an opening in the mother cell wall, and after coming 

 to rest forming 1-16 new colonies. 



1. E. RICHTERI (Schmidle) Lagerheim, 18950., p. 20, PI. I, 

 figs. 12-27 J Euastrum Richteri Schmidle, 1894, p. 60, PI. VII, 

 fig. 25. Cells trapezoid, strongly emarginate, 5-20 X 4.5-25 n ; 

 colonies 10-40 X 6-25 fi; zoospores 5 p. diam. Fig. 19. Wis., 

 G. M. Smith. Europe. 



Page 187, add, 



GEMINELLA Turpin, 1828, p. 329. 



Cells ovoid-cylindric to short-cylindric, normally in a single 

 series in a wide, homogeneous gelatinous sheath ; chromato- 

 phore zonate with one pyrenoid ; asexual reproduction by cell 

 division, the daughter cells usually remaining approximate ; 

 zoospores unknown ; akinetes in some species. 



The generic name Hormospora is antedated by Geminella. It 

 is now generally recognized that in addition to the Hormospora- 

 forms assumed by some species of Ulothrix, etc., there are 

 autonomous forms with the characters of the genus. It is a 

 question whether Radio/Hum is distinct ; the only distinguishing 

 character now available is the structure of the sheath, homo- 

 geneous or longitudinally laminate in Geminella, transversely 

 in Radio/Hum. Wille, 1909, p. 72, has Hormospora and Radio/Hum 

 as sections of Geminella. In none of the species is the life his- 

 tory fully known, so for the present the two genera are retained. 



KEY TO THE SPECIES OF GEMINELLA. 



i. Cells transversely elongate. i. G. scalariformis. 



i. Cells longitudinally elongate. 2. G. interrupta. 



Page 188, for HORMOSPORA SCALARIFORMIS read, 

 GEMINELLA scalariformis G. S. West ms. ; Hormospora 



scalariformis G. S. West, 1905, p. 282, PI. CCCLXIV, figs. 6-7. 



Fig. 21. 



After description of GEMINELLA SCALARIFORMIS, add, 

 Forma MARINA G. S. West in Collins & Hervey, 1917, p. 31. 



Cells proportionally longer, sheath more homogeneous. In salt 



water, Bermuda, Collins. 



2. G. INTERRUPTA Turpin, 1828, p. 329, PI. XIII, fig. 24 ; 

 emend. Lagerheim, 1883, p. 68, PI. I. figs. 30-35. Cells 5-7 /x 

 diam., 6-15 /. long, in a single series ; sheath 16-18 p. diam. ; 

 cells from recent division remaining approximate ; akinetes 

 9-10 p. diam., to 15 /x long, with thick, dark wall. Wis., G. M. 

 Smith, New Buffalo, Mich., Transeau. Europe. 



