296 University of California Publications in Botany [Vol.8 



Crouan, loc. cit.; Iluber, Contributions des Chaetophorees, 1892, 

 p. 294 et seq., pi. 11, f. 4-6; Collins, Green Alg. N. A., 1909, p. 286; 

 Wille, Nachtrage, 1909, p. 89. 



We feel compelled to refer here a plant found in abundance on a 

 species of Ixiiirencia at Pacific Grove, California, in July. In gen- 

 eral appearance, in structure, in dimensions of the cells and manner 

 of peripheral growth, the specimens correspond exactly with the 

 figures and description of Huber (loc. cit.) for the type material of 

 Ulvella Lens. Our plants, however, have only been detected, thus 

 far, as epiphytes. "We have seen, in our preserved material, the central 

 cells both empty and divided into 8 rounded bodies, probabh' zoo- 

 spores. Unfortunately we have not preserved specimens in a con- 

 dition suitable for the study of the number of nuclei in the cells. 



31. Pseudulvella Wille 



Thalli forming small disks, composed of radiating filaments closely 

 placed, coalescent and finally more or less loosely pluristratose towards 

 the center, unistratose and more or less free and dichotomous towards 

 the periphery ; cells uninucleate, with a single parietal chromatophore 

 containing a single pj^renoid; zoospores 4-ciliated. 



Wille, Nachtrage, 1909, p. 90. Ulvella Snow, Ulvella americana 

 1899, p. 309 (in part). 



The genus Pseudulvella is said to differ from Ulvella in that the 

 cells of its species have onl}^ a single nucleus, the chromatophore has 

 a single pyrenoid and the zoospores are 4-ciliated. It is said to differ 

 from Pseudopringsheimia in the lack of rhizoid-like filaments which 

 penetrate the host. It is placed by Wille {loc. cit., p. 79) among the 

 genera whose species lack hairs, although Snow (1899, p. 310) says 

 that ''in quite a number of cases, long gelatinous hairs extended from 

 the surface" in the type species, Ulvella americana Snow. This state- 

 ment as to hairs undoubtedly led Collins (1909, p. 289) to refer the 

 Ulvella americana Snow to Chaetopeltis. Since Snow does not figure 

 the hairs and the statement seems little convincing, we are inclined 

 to follow Wille in presuming that no hairs are present. 



Key to the Species 



1. Basal layer of more or less distinctly radiating filaments 2 



1. Basal layer distinctly parenchymatous 3. P. applanata (p. 298) 



2. Radiating filaments loosely coalescent ....1. P. prostrata (p. 297) 



2. Radiating filaments closely coalescent 2. P. consociata (p. 297) 



