296 Vniversity of California Publications in Botany [Vol. 7 



mcti-ic. sliarply aiij^'Icd, 6-7.5/1 diam. ; chroinatopliore covering the cell 

 wall provider with one pyi'ciioid ; zoosporangia (?) slightly modified 

 siii'face cells; reproduction unknown. 



Growing on the shells of Littorina planaxis Nutt. Central Cali- 

 fornia. Type no. ;3597, Gardner. 



Littorina planaxis Nutt. is very abundant in small tide pools and 

 in moist places along high-tide level from Sitka to San Diego. 

 Pseudulvclla applanata has been studied only on material found along 

 the coast of central California, but it is presumed to have a much 

 wider distribution. 



Its presence on the host is readily recognizable by the expanded, 

 grass green, glossy appearance of the surface of the shell. Micro- 

 scopically it may readily be distinguished from all other described 

 species of the genus by its very small, closely compact, parenchymatous 

 cells, and the seeming absence of radiating filaments composing the 

 basal layer. It spreads over the host by tangential and by radial 

 divisions of the peripheral cells, at least the process can thus be de- 

 scribed when the plant is of considerable size. It probably starts on 

 the very young host, and doubtless many plants early coalesce to 

 form a confluent thallus. We have not been able to ascertain the 

 nature of the early developmental stages, although very small shells 

 have been examined. 



Reproductive bodies have been seen to escape from the surface 

 cells. Whether these are zoospores or gametes, the number of cilia 

 they possess and their behavior after escaping are subjects for further 

 investigation. 



The three species of Pseudulvella known from the M^estern coast 

 of North America may be arranged, so far as the basal layer is con- 

 cerned, in the following sequence : P. prostrata, with distinctly 

 radiating basal filaments which branch rather frequently and which 

 are comparatively loosely coalescent ; P. cmisociata, with indistinctly 

 radiating ba.sal filaments closely coalescent; and P. applanata with a 

 parenchymatous basal layer. 



Pseudulvella consociata sp. nov. 



Plate 24, figures 4-6 



Thallo magnitudine et peripheria irregulari, 100-1 40/a crasso, per 

 filamcnta ii'rcgularia et radiantia augeseente ; filamentis mox coale- 

 scentil)us <'t iJai'fnchymaticis, atroviridi ; filamentis erectis dense ad- 

 haerentibus. T-lO/x diam., cellulis prope cylindricis, forma leviter 

 irregularibus, 1-2-plo diam. longioribus; zoosporangiis (?) terminal- 

 ibus. ])yrifoi'ini])us us<|ue ad sphaericis, 8 zoosporas emittentibus. 



