76 SMITH: TETRADESMUS, A NEW COENOBIC ALGA 
The triple stain of Flemming gave the best differentiation, and all 
drawings are from preparations made in this manner. 
I wish to express my thanks here to Professor Charles E. Allen 
for kind criticism and keen interest shown during the progress of 
this work and preparation of the manuscript. 
DIAGNOSIS 
The alga in question normally occurs in the form of four-celled 
colonies. The characteristic feature of the arrangement of the 
cells is that when viewed from the side they are seen to be in two 
tiers, while in Scenedesmus, apparently the most nearly related 
form, the cells are all in a single plane. The shape of the cells 
varies somewhat with their age, the mature ones being more ovoid. 
The following are the descriptions of the genus and species: 
Tetradesmus gen. nov. 
Colonies free, of 4 cells, rarely 1 or 2; cells in two planes, 2 cells 
in each plane, joined along the longer axes, ovoid with pointed ends; 
chlorophyl present throughout the cell, pyrenoid single. Repro- 
duction by autocolonies inside of old cell wall, liberated by rupture 
of mother cell wall. 
Coenobia segregata, e cellulis quaternis (rarius 1-2). Cellulae 
binae latere longiore in seriem duplicem conjunctae, ovoideae 
utroque polo acutae, homogeneae chlorophyllosae, et pyrenoide 
singulo praeditae. Propagatio fit autocoénobiis intra cellulam 
matricalem quae membranae ruptura prodeunt. 
Tetradesmus wisconsinensis sp. nov. 
Cells ovoid with sharply pointed ends, 4-5.8 by 12-14.5 mu. 
Hasitat: Floating in sluggish streams and lakes; Madison, 
Wisconsin. 
Cellulae ovoideae utroque polo acutae, 4-5.8 w X 12-14.5 mp. 
Hasirat: In rivulis lente fluentibus et lacubus libere natantes. 
Madison, Wisconsin. 
The characters described above are sufficient, in my opinion, 
to warrant the assumption that we have a new genus. The 
objection may be made that this is merely a cultural form of 
enedesmus acutus Meyen; for according to Chodat (3), Chodat 
