110 Cushman: New England species of Closterium 



vacuole containing one or more crystals of calcium sulphate in 

 continuous motion. Since the desmids were first known, these 

 granules have been a point of interest. 



The zygospores of Closterium are usually formed between the 

 parent cells and are free. In certain cases the zygospores are 

 paired but usually single and globose. As a rule the zygospores 

 are smooth but in a few species there are spines. In a few species 

 cruciform or quadrate zygospores are formed and the cells remain 

 attached for some time. 



Enough synonymy is given under each species to refer to 

 published figures in accessible works and to straighten out many 

 of the New England records already published. The figures given 

 are camera-lucida drawings from specimens. The figures given 

 by Wolle were in many cases rather too conventionalized to repre- 

 sent clearly the form he had under observation. In all, about fifty 

 species of this genus are now known from New England. Those 

 not previously recorded are indicated by an asterisk. The meas- 

 urements and short description are based entirely upon observed 

 specimens from New England. 



As given here, length means the length of a straight line drawn 

 between the apices — not the length of the axis of the cell. 

 Breadth means the diameter across the middle of the cell ; where 

 the cross-section of the cell is elliptical, as it is in some of the 

 straight forms, the greatest diameter is given. Records for which 

 I have seen specimens are followed by an exclamation point. In 

 other cases the author's name is given in parentheses. 



It will be noted that many of the species are recorded only 

 from southeastern Massachusetts and Rhode Island. Collections 

 from this region were especially rich in Closterium, both in number 

 of species and individuals. 



i. Closterium Cynthia DeNot. 



Closterium Cynthia DeNot. Elem. Stud. Desm. Ital. 65, 

 7. /• 71. 1867. — Johnson, Bull. Torrey Club 22 : 291. 

 2 39- /• J- 1895.— W. & G. S. West, Brit. Desm. I : H.3- 



pL 11. f. i- 3 . i 9 o 4 . 



Cells small, about 8-10 times as long as wide, strongly curved, 

 apices obtusely rounded; cell-wall yellow-brown with about 13' 

 10 striae visible across the cell 



