144 University of California Puhlications in Botany [Vol. 8 



The names Palmellaeeae and Palmelleae are used with different 

 intent and to different extent by various writers and are interchange- 

 able wholly or in part with other family designations. It has seemed 

 best to follow West as to the usage in this account. The fundamental 

 idea is that of the colony the cells of which are held together by 

 means of the mucilaginous material produced by the transformation 

 of the outer walls. Some of the colonies are microscopic while others 

 are of considerable size reaching a length (e.g., in some species of 

 Tetraspora) of 15 to 20 centimeters. The mucilaginous modification 

 may be general or it may be localized on each cell wall, and the shape, 

 as well as the size, of the colony may thereby be influenced. The cells 

 possess a single parietal chromatophore with a single pyrenoid. 

 Colonies may split up and multiply the plant. Reproduction by 

 zoospores and planogametes is the rule. In zoospore formation several 

 (4 or 8) may arise in a zoosporangium or an ordinary cell may be 

 transformed directly into a zoospore. This latter method, as well a^ 

 the general cell structure and colony formation, points directly toward 

 relationship with the Volvocaceae. 



1. CoUinsiella S. and G. 



Frond gelatinous, solid or later hollow, composed of pyriform cells, 

 on dichotomous, gelatinous stalks tapering downward from the cells; 

 all enclosed in the general gelatine ; chromatophore band-shaped, with 

 one large pyrenoid ; the terminal cells become the zoosporangia ( ? ) 



Setchell and Gardner, Alg. N.W. Amer., 1903, p. 204. 



There is a reason for difference of opinion as to whether CoUins- 

 iella is to be retained as an independent genus or merged with the 

 genus Echallocystis Bohlin. It has seemed best to place the discussion 

 under the single species known from our coast. 



CoUinsiella tuberculata S. and G. 

 Plate 10, figs. 4-10 

 Colonies rugose-tuberculate, 2-4 mm. diam., dark green, gelatinous, 

 firm, attached by a broad base ; cells pyriform, 5-12/^ diam., 12-20/a 

 long ; branches repeatedly dichotomous, proceeding in two planes per- 

 pendicular to each other and to the surface of the colony, some of the 

 cells of the dichotomies pushing forward, forming the cortex, leaving 

 behind the translucent, stalklike, gelatinous cell walls, while growth 



