458 University of California PuUications in Botany [Vol. 6 



Cells solitary or contiguous, spherical, 8-16fi diam., pale blue- 

 green ; cell wall thin, hyaline ; protoplast finely granular ; gonidangia 

 spherical, 8-16jli diam. ; gonidia angular at first, becoming spherical 

 at maturity, 2.5-3/a diam., formed by simultaneous division of the pro- 

 toplast, escaping by dissolution of the entire gonidangial wall. 



Growing on various species of algae in the littoral belt, frequently 

 in salt marshes. Ranging from Whidbey Island, Washington, to cen- 

 tral California. The type material was found growing on a species of 

 Lyngtya. Lands End, San Francisco, California. Type no. 1906, 

 Gardner. 



Xenococcus ScJioushoei Setchell and Gardner, Alg. N. W. Amer., 

 1903, p. 180; Collins, Holden and Setchell, Phyc. Bor.- Amer. (Exsicc), 

 no. 554 (not Thuret, in Bornet and Thuret, 1880, p. 73-77, pi. 26, 

 fig. 1-2). 



Derniocarpa sphaerica is the plant that has commonly passed for 

 Xenococcus Sclioushoei on the Pacific coast of North America. Ex- 

 amination of a bit of the type material of Schousboe's Coleonema 

 arenifera, upon which Thuret founded the genus, shows that the 

 Pacific coast plant belongs to a different genus. Xenococcus Schous- 

 hoei, as described and figured by Thuret, has increase in the number 

 of individuals by means of vegetative cell divisions. This is the con- 

 dition in which Schousboe found the type material ; the plants being 

 young the gonidial stage had not yet appeared. Our plant, which has 

 passed under the name of X. ScJioushoei, does not divide vegetatively, 

 and hence belongs to the group, of which Derniocarpa may be taken as 

 a tj^pe, in which there is increase only by the formation of gonidia, 

 instead of the group, of which Pleurocapsa may be taken as a type, in 

 which there is increase by both vegetative cell divisions and by gonidia. 



Kirchner (1898, p. 58) and Forti (1907, pp. 119, 120) recognize 

 five genera of Chamaesiphonaceae which have no vegetative cell divi- 

 sions and which reproduce exclusively by gonidial formation. These 

 are Cyanocystis Borzi (1882, p. 314), Derniocarpa Crouan (1858, p. 

 70), Clastidium Kirchner (1880, p. 195), Chamaesiphon A. Br. & 

 Grun. (1865, p. 148), and Godlewskia Jancz. (1883, p. 227). Kirchner 

 separates the first three genera from the last two because of the 

 simultaneous division of the whole protoplast of the gonidangium into 

 gonidia, whereas in the last two genera the gonidia are abstricted 

 successively from the apex of the gonidangium, the basal portion 

 always remaining sterile. Forti adopts this entire arrangement ex- 

 cept the statement of the simultaneous division of the protoplast. 



It is necessary to modify Kirchner 's statement in regard to the 

 simultaneous division of the protoplast in Derniocarpa since I have 



