Myxophyceae 47 



Genus PLEUROCAPSA Thuret in Hauck. 

 Die Meeresalgen Deutschlands and Oesterreichs. 515. 1885. 



Colonies usually crustaceous, made up of vegetative cells and gonidan- 

 gia; plants united in short filaments, parallel or scarcely distinct, radiating, 

 often dichotomously divided; cells spherical or angular, rarely oval or 

 polyhedral; cell contents blue-green, olive, yellowish or violet; gonidangia 

 furnished with thick sheaths, producing numerous, spherical gonidia; repro- 

 duction by cell divison in three directions, by division of filaments into 

 fragments, and by gonidia formed by division of the contents of a gon- 

 idangium. < 



I Cells arranged in straight rows; growing in fresh water 



PI. concharum 



II Cells not arranged in straight rows 



1 Growing in hot water; cells 4-6 mic. in diameter 



PI. caldaria 



2 Growing in salt water 



(i) Cells S-20 mic. in diameter; cell contents golden yellow, fawn- 

 colored or dull violet PI. fuliginosa 



(2) Cells 10-13 niic. in diameter; cell contents violet 



PI. amethjrstea 



(3) Cells up to 15 mic. in diameter; cell contents dull blue or slate 



color PI. crepidinum 



107. Pleurocapsa concharum Hansgirg. Phys. und Alg. Mittheil. pi. i. 



f. ii-iS. 1890. De Toni. Syll. Algar. 5: 122. 1907. 



Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 22. no. 1031. 1903. 



Colonies minute; tegument moderately thin, colorless; cells 4-17 mic. 

 in diameter, 4-34 mic. in length, spherical, oval, ellipsoid or angular from 

 mutual pressure, united into short, often irregularly dichotomous filaments 

 of four to ten cells each, or into somewhat spherical masses; cell contents 

 very finely granular, dull bluish or olive green; gonidangia 12-20 mic. in 

 diameter, containing 8-32 gonidia; gonidia 3-4 mic. in diameter, spherical. 



California. On shells. Mountain Lake. San Francisco. June 1902. (Oster- 

 •hout and Gardner). 



108. Pleurocapsa caldaria (Tilden) Setchell in Collins, Holden and 



Setchell. Phyc. Bor.-Am. Fasc. 18. no. 851. 1901. De Toni. 



Syll. Algar. 5= 123- 1907. 

 Tilden. Observations on some West American Thermal Algae. Hot. 

 Gaz. 25: 94. pi. 8. f. 18. 1898; American Algae. Cent. III. no. 283. 1898. 

 (Protococcus botryoides f. caldaria Tilden) ; American Al- 

 gae. Cent. II. no. 198. 1896; Bot. Gaz. 25: 104. pi. 8. f. 21. 1898. (C h r o o c o c- 

 cus variusA. Br.) 



Plate III. fig. I. 



Plant mass pale or yellowish green; sheaths thin, homogeneous, hyaline; 



