HOW TO KNOW THE FRESH-WATER ALGAE 



156a Cells subcylindrical or ovoid, small, less than 4.5 ^ in diameter, 

 with a parietal plate-like chloroplast at one or both ends. Fig. 

 116 NANNOCHLOR1S 



Fig. 116. Nannochloris bacillaris Naum. 



These tiny cells are solitary and are 

 without a gelantinous sheath. They are 

 able to undergo cell division in vegeta- 

 tive reproduction and hence are assign- 

 able to the Coccomyxaceae along with 

 Elakatothrix (Fig. 38) and Dactylothece (Fig. 

 Figure 116 ^7). It is a frequenter of laboratory cul- 



ture. 



156b Cells different in size and shape, or with a different type of 

 chloroplast 157 



157a Cells bearing spines or decorated with ridges 158 



157b Cells without spines or decorations 164 



158a Spine length greater than the diameter of the cell 159 



158b Spine length less than the diameter of the cell; wall usually 

 decorated with a network of thickenings 163 



159a Spines not tapering from base to apex, long and slender 161 



159b Spines tapering to apex, long and slender, or short and stout. . 160 



160a Spines stout, broad at the base and tapering. Fig. 117 



ECHINOSPHAERELLA 



Fig. 117. Echinosphaerella limnetica G. M. Smith. 



This is a relatively rare species from the 

 euplankton. In making identification care should 

 be used in distinguishing the single parietal 

 chloroplast by which the plant may be differ- 

 entiated from some of the spiny zygospores of 

 desmids (in which the cell content appears 

 dark and massive, with no definitely shaped 

 Figure 117 chloroplast distinguishable). 



78 



