476 University of California Publications in Botany [Vol.8 



gTOwtli and dichotomous branching, by the splitting' of the apical cell, 

 thus forming a continuous monostromatic layer of cells. Beginning 

 in the center, practically every cell in each radiating filament of the 

 basal lawyer gives rise successively to an erect filament, about two-thirds 

 of which are fructiferous, the others remaining sterile. A very large 

 majority of the gametangia, are sessile or on short pedicels, thus 

 occupying a zone near the creeping filaments, a myrionematoid char- 

 acter, but the remainder of the filaments continue to grow and attain 

 a length of SOO/x to 400/x. Some of these filaments are terminated by 

 relatively short gametangia. This is one of several species with this 

 general method of development which has been found growing only 

 on the above mentioned host, differing from each other and from the 

 type of the genus, C. gracile Kuckuck, in the size of the plant as a 

 whole, in details of dimensions of their parts, in the presence or absence 

 of zoosporangia and hairs, in the position of the gametangia, and in 

 the relative amount of sterile filaments. It seems to form a fairly 

 compact group but with overlappings, however, in th^ genera Stre- 

 hlonema, Myrionema, and Hecatonema. 



4. Compsonema fructuosum S. and G. 



Fronds forming circular or somewhat irregular cushions, 4-5 mm. 

 diam. ; prostrate portion composed of tortuous creeping filaments fol- 

 lowing closely the irregularities of the surface of the host ; erect fila- 

 ments unbranched, densely crowded, 190-230/x long, cells cylindrical, 

 8-9ju, diam., 2-4 times as long below, 1-2 times above ; chromatophores 

 band-shaped ; hairs absent ; zoosporangia sparse, broadly clavate, 

 terminal on short pedicels from the creeping filaments, 55-65/x (up to 

 100/x) long, 22-28/A broad; gametangia terminal on erect filaments, 

 cylindrical to slightly fusiform, blunt, 80-120/;. long, 12-16//, broad; 

 loculi 2-4-seriate. 



Growing on the pneumatocysts of Nereocystis Luetkeana. Tomales 

 Bay, Marin County, California. 



Setchell and Gardner, Phyc. Cont. Ill, 1922, p. 355, ph 36, fig. 2. 



Compsonema fructuosum departs from the type of the genus, C. 

 gracile Kuckuck (1899, p. 90, pi. VI (12), figs. 6-9), in having a differ- 

 ent host, no hairs, fewer and shorter sterile filaments, more gametangia, 

 and in having differences in details of measurements. In the abun- 

 dance and position of the fruit and in the definite circular thallus 

 with compact monostromatic basal layer of filaments, it approaches 



