462 University of California Publications in Botani/ [Vol.8 



on the other part of the host is a mixture. In height of gametangia 

 forma simplicissimum approximates to forma seriata Reinke (1889, 

 p. 46), but has no true hairs so far as we have been able to observe 

 from the examination of many specimens from different localities. At 

 times the individuals are very numerous on the host, so much so as to 

 interfere with each others' growth. In one collection (Gardner, 

 no. 4651) they are completely confluent over several square inches, 

 and the outline of the individuals can be detected only by staining 

 and by microscopic examination. 



7. Myrionema foecundum f. subulatum S. and G. 



Basal filaments attached by numerous awl-shaped rhizoicls, 2-4 

 cells long, penetrating between the cells of the host; zoosporangia, 

 "ascocysts" and true hairs unknown. 



Growing on the sporophylls of Nereocystis Luetkeana. Near the 

 ' ' Cliff House, ' ' San Francisco, California. 



Setchell and Gardner, Phyc. Cont. II, 1922, p. 337, pi. 33, figs. 1-3. 



Forma subulatum is very similar to forma simplicissimum. The 

 gametangia average slightly larger and are usually more blunt. There 

 are no so-called "ascocysts" present. The chief distinction is the 

 presence in this form of numerous awl-shaped rhizoids, found in no 

 other form of the species, so far as we have been able to ascertain. 



8. Myrionema foecundum f. ramulosum S. and G. 



Fronds forming small circular cushions, 1-3 mm. diam. ; erect 

 filaments slightly branched above, 55-65/x long ; cells of the erect fila- 

 ments 5.5-6.5/* diam., quadrate, terminal cell frequently 2-3 times 

 as long; zoosporangia, "ascocysts" and true hairs unknown; all of the 

 erect filaments transformed into gametangia. 



Growing on the pneumatocysts of Nereocystis Luetkeana. Friday 

 Harbor, San Juan Island, Washington. 



Setchell and Gardner, Phyc. Cont. II, 1922, p. 337, pi. 33, fig. 8. 



This form of 31. foecundum differs from the other forms of the 

 species in having secund "proliferations" near the outer ends of 

 many of the gametangia. 



