BY G. 1. PLAYFAIR. 523 



Var. iNEKMis, n.var. (Pl.liii., f.8, 9). 



Formse typicae consimilis (vel ovalis) sed major, setis nullis. 



Cell. long. 12-16; lat. 7-10 /x. 



Numbers of this form were observed free. They are not newly 

 formed aplanospores, but well-grown specimens, on which the 

 setfe have not yet developed. This is evident from the fact that, 

 in dimensions, they tally exactly with the verticillate forms. It 

 is probably the greater strength of the cell that causes the larger 

 number of setae, the smaller cells of every shape generally pos- 

 sessing only two or at most three at each pole. In no case have 

 I observed aplanospores furnished with even rudimentary setae 

 while within the mother-cell; probably the higher temperature of 

 our waters brings about the early solution of the containing 

 membrane. 



Var. GRACILIS mihi(i/. genevensis Chod., pro 'parte, I.e., f.2). 



Forma gracilior, elliptica, setis saepe minime divergentibus. 



Cell, matric. long. 14-15, lat. 10-11 ji. 



Cell. long. 8-10, lat. 3-3^, setae ad 20 /x. (PI. liii., f.lU Vl). 



A very distinct form. A forma decussata mihi was noted, with 

 the pairs of setae decussating. In this variety, the setae are 

 generally quite straight, and so widely divergent often as to l>e 

 almost parallel. 



Var. suBGLOBOSA(Lemm.). 



Cell. long. 8; lat. 7 /x. 



Only one specimen was observed free, but, in cells with four 

 aplanospores, the latter appertain in shape indiscriminately to var. 

 subglobosa and var. acuminata. No tubercles at the base of the 

 setae. 



Var. ACUMINATA, n.var. (Pl.liii., f.l3-19j. 



Aplauosporis ellipticis utroque polo acuminatis; lateribus arcu- 

 atis ad apices rapide convergentibus; pyrenoidibus minutis binis 



Cell, matric. long. 14-22; lat. 14-18J- /x. 



Apian, long. 7-14; lat. 4-10; seta? ad 33 /x. 



Var. acuminata is a very distinct shape, but, at the same time, 

 it is only an alternative form of the type. The same twin-forms 



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LI B R AR Y!3d| 



