406 University of California Puhlications in Botany ' [Vol. 8 



Forming low patches on Postelsia pahnaeformis. Observed only 

 on the coast of central California, but it probably has a much wider 

 distribution. 



Collins, in Collins, Holden and Setcheli, Phyc. Bor.-Amer. 

 (Exsicc), no. 1384. PylaieUa {Panthocarpus) Postehiae Skottsberg, 

 Notes on Pac. Coast Alg*. I, 1915, pp. 153-164, jjls. 17-19. Leptonema 

 fasciculatum Saunders, New and Little Known Brown Algae, Erythea, 

 vol. 7, 1899, p. 38, figs. 5-7 (not of Reinke). 



Saunders (loc. cit.) reports the species as growing on the shells of 

 the mollusk, Mytilus, in the. vicinity of Postelsia. We have not seen 

 it growing elsewhere than on the above named host. The gametangia 

 are intercalary rather than terminal. There are always a few terminal, 

 assimilating cells which do not metamorphose into gametangia. The 

 creeping filaments do not seem to penetrate the uninjured host at 

 any point, but if the surface cells of the host become bruised or in 

 any way destroyed, the extending filaments follow the irregularities 

 of the surface, and at times even penetrate a short distance among 

 the cells beneath. 



4. Pylaiella tenella S. and G. 



Fronds widely diffused, attached by small, short, branched, con- 

 torted filaments, unbranched, 0,5-0.75 mm. high, long-attenuate 

 upwards, not piliferous; cells 7-lOja diam., 1-2.5 times as long as the 

 diameter ; chromatophores, when young, a parietal broken band nearly 

 filling the cell, later separating into several distinct pieces; zoo- 

 sporangia long-catenate, subterminal, numerous assimilating cells in 

 the series forming two or four zoosporangia by longitudinal divisions ; 

 gametangia subterminal. 



Growing on Pleurophycus Gardneri Setcheli and Saunders, the 

 plants forming minute tufts, which later become confluent. Neali Bay, 

 near Cape Flattery, Washington. 



Setcheli and Gardner, Phyc. Cont. V, 1922, p. 385, pi. 42, figs. 9-11. 



This Pylaiella is the most diminutive of all the known species of 

 the genus, rarely attaining the length of one millimeter, its nearest 

 rival in this respect being P. nana of Kjellmaii, from tlie Norwegian 

 Polar Sea. It differs from that species in size, being only about one- 

 half as high, in not being branched and in having subterminal game- 

 tangia in a long series, instead of terminal branched ones as described 

 and figured by Kjellman for P. nana. The double and quadruple 

 zoosporangia observed in this species, formed by longitudinal and 



