1920] Setchell-Gardner: Chlorophyceae 297 



1. Pseudulvella prostrata (Gardner) S. and G. 



Plate 11, figs. 1, 2 

 Thallus 2-3 mm. diam. consisting of 2-3 layers of cells in the 

 center, but of a single layer at the margin, formed by branching fila- 

 ments growing out radially on the host, coalescing in the central part 

 of the thallus but free from each other around the margin, and 

 adhering very firmly to the host; filaments branched, 6-7 fx diam., 

 nearly uniform in diameter throughout their entire length; cells 

 quadrate in the center of the thallus, those at the outer ends of the 

 filaments 1.5-2.5 times as long as broad ; color very dark green ; end 

 cells blunt, each containing a single peripheral chromatophore and 

 one pyrenoid. 



Growing on the basal portion of Iridae<i laminarioides. Central 

 California (Lands End, San Francisco). 



Setchell and Gardner, Phyc. Cont. I, 1920, p. 295. Ulvella pros- 

 trata Gardner, New Chlorophyceae, 1909, p. 373, pi. 14, f . 1, 2 ; Collins, 

 Green Alg. N. A., 1909, p. 287 ; Collins, Holden and Setchell, Phyc. 

 Bor.-Amer. (Exsicc), no. 1629. 



Although we know too little of the Ulvella prostrata Gardner both 

 from the point of view of its cytology and of the nature of its zoo- 

 spores, it cannot remain in Ulvella because of the presence of a 

 pyrenoid in the chromatophore. It does not possess the penetrating 

 rhizoidal filaments supposed to be characteristic of Pseudopriiuj- 

 sheimia. It does, however, resemble Pseudulvella artierioana (Snow) 

 Wille sufficiently closely in its general structure to be referred to 

 the same genus for the present at least. 



2. Pseudulvella consociata S. and G. 



Plate 19, figs. 4-6 



Thallus irregular in size and in outline, 100-140/x, thick, increasing 

 b}' irregular and obscurely radiating filaments early coalescing and 

 becoming parenchymatous; color dark green; erect filaments firmly 

 coalescent, 7-10/* diam., cells nearly cylindrical, slightly irregular in 

 form, 1-2 times as long as the diameter; zoosporangia (?) terminal, 

 pyriform to spherical, producing 8 zoospores. 



Growing on the shells of Ilyanassa ohsoleta Say. Central Cali- 

 fornia (Bay Farm Island, Alameda). 



Setchell and Gardner, Phyc. Cont. I, 1920, p. 296, pi. 24, fig. 4-6. 



