Rhodora 
JOURNAL OF 
THE NEW ENGLAND BOTANICAL CLUB 
Vol. 10. June, 1908. No. 114. 
A SYNOPSIS OF THE NEW ENGLAND SPECIES OF 
MICRASTERIAS. 
JOSEPH A. CUSHMAN. 
THE genus Micrasterias includes some of the largest and most 
showy of the Desmids. The cells are usually disc-shaped and sub- 
cireular in outline, cut into many divisions by more or less radiately 
arranged incisions. Species are often very common in certain areas, 
but many of them seem limited to lakes or bodies of water of some 
size. 'lhere are twenty-two species given here for New England and 
this number is probably fairly complete. There are eighteen species 
given in the Wests’ British Desmids. Two of the British species 
have not been found as yet in America and a third one while reported 
from the United States has not been found in New England. On the 
other hand eight of the species given here have not been found in the 
British Isles and certain of these seem to be peculiar to America. 
Some of these eight, such as M. foliacea, M. Nordstedtiana and M. 
muricata are very different in type from others of the genus. The 
figures given in Wolle’s Desmids of the United States were much 
conventionalized and therefore it is often hard to say just what Wolle 
actually saw. The same is true of the reported localities where the 
identification of the species depended upon Wolle's figures. “Іп this 
genus however this difficulty is much less than is the case of certain 
other more difficult genera. As shown by Johnson (Bot. Gaz. 1894) 
the species of Micrasterias are very variable. According to the Wests 
this variability is much greater in American than in British specimens. 
However as many of these so called varieties are often seen forming 
one semicell of a specimen, the other semicell of which is typical, it 
seems hardly wise to recognize them as good varieties. 
Many of the species are represented by mounted slides in my own 
