452 University of California Publications in Botany [Vol. 8 



15. Streblonema myrionematoides S. and G. 



Fronds microscopic ; prostrate portion very poorly or scantily 

 developed, penetrating only slightly among the two or three outer 

 layers of cells of the host ; erect filaments more or less f asciculately 

 branched at the surface of the host, 65-80//, long, mostly fructiferous, 

 hairs few ; cells of the penetrating filaments 4-5/i. diam., irregular in 

 shape ; zoosporangia unknown ; gametangia numerous, cylindrical, 

 50-65/x long, 4.5-6. 5/a broad ; loculi uniseriate. 



Growing on the blade of Laminaria Andersonii Farlow. Moss 

 Beach, San Mateo County, California. 



Setchell and Gardner, Phyc. Cont. V, 1922, p. 387, pi. 44, fig. 7. 



It is an extremely perplexing problem to decide upon the generic 

 position of forms such as the one described above. It has close affini- 

 ties with the three genera, Streblonema, Ectocarpus and Myrionema. 

 The erect fronds exterior to the host and more or less branched, with 

 relatively scanty attaching portions, constitute the vegetative portion 

 of an Ectocarpus of microscopic size. The gametangia are strictly 

 those of a typical Myrionema, but there is lacking the disk-shaped basal 

 layer of filaments spreading out on the surface of the host, character- 

 istic of that genus. The extremely reduced character of the penetrat- 

 ing portion does not speak well for the genus Streblonema. On the 

 whole, we feel that with our present criteria for these genera it best 

 agrees with the characters of the genus Streblonema, where we have 

 placed it. It penetrates the uninjured host, but only to a slight depth. 

 The plants, however, are usually so congested that their growth soon 

 crowds the surface layer of the host cells to such an extent that they 

 die and disintegrate, there being no evidence that the associate pene- 

 trates them and absorbs their material. The palisade-like stratum of 

 gametangia suggests very strongly the Myrionema character which is 

 the reason for the specific name. 



16. Streblonema investiens (Collins) S. and G. 



Fronds occupying indefinite areas on the host ; creeping filaments 

 irregularly branched, often curving outward and bearing on the out- 

 side short, simple, or sparsely branched filaments; hairs sparse; cells 

 of creeping filaments 5-8/x diam., 1-2 (up to 4) times as long, swollen 

 or cylindrical; cells of the ramuli 6/x diam., 1-2 times as long; cells 

 of the hairs 8/x diam. ; chromatophores discoid, small, several in a 



