THE GREEN ALGAE OF NORTH AMERICA 155 



Characters of the genus ; appearing under two forms : 



Var. MAJOR Moore, 1901, p. 311, PI. X, figs, i and 2; P. 

 B.-A., No. 1315. Cells 70-150 /A diam. 



Var. MINOR Moore 1901, p. 311, PI. X, fig. 3. Cells 30-50^ 

 diani. Greenland, Me., Mass., Conn. Europe. 



The unusually large size of this unicellular alga, the perfect 

 spherical form, bright green color, and varied, often quite sym- 

 metrical arrangement of the small chromatophores, make it an 

 interesting object. Chodat, 1895, describes forms and modes 

 of propagation which if confirmed would change its position 

 among the green algae, and also identify, as stages of growth, 

 other supposedly distinct forms. The long continued and care- 

 ful studies by Moore failing to show anything of the kind, the 

 present position seems the best for it. 



2. EXCENTROSPHAERA Moore, 1901, p. 322. 

 Cells uninucleate, solitary, free, large ; spherical, ellipsoidal, 

 or sometimes irregular and angular ; chromatophores large, 

 angular, more or less radiately arranged, covering the entire 

 wall, each with numerous minute pyrenoids ; asexual reproduc- 

 tion by numerous aplanospores, escaping by an opening in the 

 cell wall, and increasing in size until the normal dimensions are 

 reached. Fresh water. Only one species. 



E. VIRIDIS Moore, 1901, p. 322, PI. XII. Cells bright green, 

 22-55 M diam., spores 2-3 /j. diam. Fig. 40. Vt., Mass. 



Europe. 



In general appearance resembling small forms of Eremosphaera 

 with which it often occurs; very likely the " Centrosphaera- 

 state " of Eremosphaera described by Chodat should really be 

 referred to this genus. 



Family 4. SCENEDESMACEAE. 



Unicellular ; cells spherical, or developing into various forms, 

 with bell-shaped chromatophore, solitary, or united by gelatine 

 in more or less regular colonies ; asexual reproduction by aplan- 

 ospores. Fresh water, rarely marine plants. 



KEY TO THE GENERA OF SCENEDESMACEAE. 



I. Living in the cells of lower animals. i. ZOOCHI.ORELLA. 



i. Not living in the cells of animals. 2. 



2. Cells contained in an extensive, gelatinous thallus. 3. 



2. No external gelatinous thallus. 5. 



3. Sporangia much larger than vegetative cells. 12. HORMOTILA. 



