36 University of California Piihlicatians in Botany [you 8 



10. Pleurocapsa Thur. 



Cells splierical or angular, and many sided by pressure, united 

 into more or less gelatinous colonies of various shapes and sizes arising 

 by cell divisions in three planes; protoplast blue-green, olive green, 

 yellowish or violet ; reproduction by vegetative cell divisions and by 

 gouidia formation. 



Thuret, in Hauck, ]\Ieeresalg. Deutschl., 1885, p. 515. 



The genus Pleurocapsa while named by Thuret was published by 

 Hauck {loc. cit.). The type specimen of the species Pleurocapsa 

 fuliginosa Hauck, the type of the genus, was collected at Trieste as 

 is evidenced by the label of the specimen in Herb. Hauck at present 

 in the possession of Dr. Anna Weber-van Bosse, through whose kind- 

 ness it has been possible to examine a fragment. The species properly 

 to be referred to Pleurocapsa are to be distinguished from those of 

 XenoGOCCUs by forming a less definite layer and by division in three 

 directions, while from those of Gloeocapsa, they differ chiefly by form- 

 ing gonidia. 



The genus Pleurocapsa, as given by Forti (1907, pp. 120-123), is 

 credited with ten species, of which one occurs on limestone walls, 

 four are marine, while five are of fresh water. The fresh water 

 species referred to Pleurocapsa, especially those described by Hans- 

 girg in his Physiologische und algoloische Mittheilungen (1890), are 

 not readily to be reconciled with the description and distinctions as 

 indicated above. They need further study. From the figures it seems 

 that their affinities tuqj possibly be rather with Radaisia, or possibly 

 even with Chaniaesiphon. Certainly no such filamentous arrangement 

 of the cells is to be found in Pleurocapsa fuliginosa Hauck or the 

 other marine species now referred to the genus. 



Key to the Species. 



1. Teguments (enclosing jelly) hyaline 2 



1. Teguments (enclosing jelly) yellowish brown 3. P. entophysaloides (p 38) 



2. Cell wall hyaline 1. P. fuli^nosa (p 36) 



2. Cell wall brownish 2. P. gloeocapsoides (p 37) 



1. Pleurocapsa fuliginosa Hauck 



Colonies forming a thin, dark crust on wood and rocks, each 

 colony being 50-100/a diam., cells 5-20/a diam., with colorless mem- 

 brane and homogeneous, golden, reddish brown or sordid violet con- 

 tents. 



Growing on piles. Seattle, Washington. 



