27(5 W. AND G. S. WEST 



had more the appearance of a short stalk than anything else, although the cells were 

 quite free and unattached. 



11 Pleurococcus frigidus sp. n. (PI. XXIV, Figs. 40-44) 



Cellulis globosis, 20-24 ^ latis, singulis vel plerumque aggregatis, intra stratum 

 Myxophycearum nidulantibus ; membrana cellularum 1.4 /< crassa; chromatophora 

 singula magna, indistincte limitata, cum granulis amylaceis numerosis vel pyrenoidibus 

 conspicuis 2-3. Propagatio gonidiis globosis 2 vel 3 intra cellulas maternas ortis; 

 diam. gonid. 10-14 i*. 



Hob. Pony Lake. 



This species was more or less abundant in a matrix consisting mostly of Phormidium 

 autumnale and other Blue-green Algae. It appears to belong to that section of 

 Pleurococcus for which Klebs founded the special genus Chlorosphcera, but so far as 

 could be ascertained from the preserved material multiplication takes place by the 

 division of the contents of the mother- cell into two or three portions, which then 

 become rounded non-motile gonidia. As these grow in size they gradually throw off 

 the old wall of the mother- cell. Each cell possesses a single nucleus, placed in a rather 

 excentric position. 



In the specimens collected in April 1908 the massive chloroplast contained numerous 

 minute granules of starch. In those obtained from the same locality in January 

 1909 the chloroplast possessed either 2 or 3 distinct pyrenoids and no scattered starch 

 granules. 



The cells are considerably larger than those of Pleurococcus angulosus Menegh., 

 and the chloroplast is not reticulated. 



12 Pleurococcus antarcticus sp. n. (PI. XXIV, Figs. 49-51) 



Cellulis globosis, 20-37 (plerumque 32) p. latis, singulis vel in familiis parvis aggre- 

 gatis inter algas Myxophycearum libere natantibus, membrana cellularum usque ad 

 2.2 /a. crassa, homogenea vel nonnunquam indistincte lamellosa ; chromatophora magna 

 parietali, indistincte limitata, ssepe cum globulis oleariis conspicuis. Propagatio ignota. 



Hob. Green Lake and Clear Lake. 



This is a large species, and, like the preceding, probably belongs to the section 

 " Chlorosphcera (Klebs) Hansg." Nothing was seen which in any way gave a clue as 

 to its methods of propagation. The chloroplast is massive, but its limitations could 

 not be de6nitely made out from the available material. It was generally partly 

 contracted from the wall at one side of the cell, and this space frequently contained 

 one, or more rarely two, globules of a fatty oil, such as occurs in Pleurococcus rufescens. 



Forma robusta. (PI. XXIV, Figs. 52-54) 



Cellulis majoribus, diam. 35-78 n, intra stratum Myxophycearum nidulantibus, 

 saepe dense aggregatis ; membr. cell. 2.5-6 p. crassa et lamellosa ; chromatophora 

 seepe distincte parietali, globulis oleariis nullis. 



