1920] Setchell-Gardner : Phycological Contributions 297 



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

 by irregular and obscurely radiating filaments early coalescing and 

 becoming parenchymatous ; color dark green ; erect filaments firmly 

 coalescent, 7-10/x 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). Type no. 4268, Gardner. 



The shells of Ilyanassa ohsoleta Say. were introduced some years 

 ago along with oysters from the Atlantic coast of North America, and 

 possibly the plant here described was introduced with the host. 



A comparison of this species with others will be found included in 

 the discussion under P. applanata. 



Pseudopringsheimia apiculata sp. nov. 



Plate 22, figures 1, 2 



Thallis minutis, 145-1 60/i, crassis, dum solitariis hemisphaericis, sed 

 frequenter dense gregariis et stratum continuum 2-3 mm. diam. for- 

 mantibus, laete viridibus; filamentis erectis 8-12jli diam., 9-12 cellulis 

 cylindricis aut leviter tumidis compositis ; zoosporangiis (?) 8 zoosporas 

 emittentibus, terminalibus, leviter tumidis, convexis usque ad conspicue 

 apiculatis ; zoosporis (?) 4-ciliatis. 



Thallus minute, 145-1 GO/x thick, hemispherical when alone, but 

 often with many crowded closely together forming a continuous 

 stratum 2-3 mm. diam. ; color bright green ; erect filaments 8-12/x diam., 

 composed of 9-12 cylindrical or slightly swollen cells ; zoosporangia 

 ( ?) producing 8 zoospores, terminal, slightly swollen, varying from 

 convex to decidedly apiculate; zoospores ( ?) 4-ciliated. 



Growing on the rhachis and the cysts of Egregia Menziesii. 

 Central California. Type no. 4361, Gardner. 



Psendopnngsheimia apiculata is closely related to P. confluens 

 (Rosenv.) Wille. The most conspicuous difference is to be found in 

 the shape and size of the zoosporangia, if the terminal reproductive 

 cells are to be designated as such. Those of P. confluens are long and 

 comparatively narrow, and produce 30 to 40 zoospores, while in P. 

 apiculata they are shorter, somewhat swollen, mostly with a pro- 

 nounced terminal projection, and produce about 8 zoospores. These 

 reproductive bodies are very small and it is exceedingly difficult to 

 determine their number of cilia. On one occasion four cilia were 

 observed, but the reproductive bodies seemed a little larger and some- 

 what more irregular in form than the average. These may have been 

 the zygotes which had been formed by the fusion of 2-ciliated gametes 

 and which had not vet come to rest. 



