480 University .of California PuhJications in Botany [Vol. 8 



extremely small size. We are inclined toward the genus Compsonema 

 as a more appropriate genus for this species than Ectocarpus on 

 account of its extensive creeping habit and prolific production from 

 the creeping filaments of nearly sessile gametangia and many sterile 

 erect filaments. It is to be found quite commonly associated on the 

 same host with several other species of Myrionemataceae. 



10. Compsonema serpens S. and G. 



Fronds forming a more or less continuous expanded stratum on 

 the surface of the host ; creeping portion composed of much contorted, 

 irregularly branched filaments; erect filaments unbranehed, or rarely 

 with a few subulate branches above, tapering slightly at the base, 

 gradually attenuated in the upper part, not pilif erous, 375-425/i, long ; 

 true hairs absent ; cells of creeping filaments cylindrical to irregular, 

 10-13ju, diam., 0.5-3 times as long; cells of erect filaments cylindrical, 

 not constricted at the dissepiments, 5.5-8.5/* diam. at the base, 10-17/x 

 diam. in the widest part, 1.25-2.5 times as long ; chromatophores band- 

 shaped, densely crowded in the young cells, more numerous and 

 separated in the old cells; zoosporangia unknoAvn; gametangia cylin- 

 drico-conical, terminal on shorter or longer pedicels from the creeping 

 filaments, rarely terminal on the long filaments, 60-130//, long, 18-28/x 

 broad. 



Growing on the sterile base of Gigartina radula f ., in company with 

 several other small algae. Cypress Point, Monterey County, California. 



Setchell and Gardner, Phyc. Cont. Ill, 1922, p. 363, pi. 39, fig. 7. 



This diminutive member of the Melanophyceae is on the border 

 line between Compsonema. and Ectocarpus. Our comprehension of 

 these two genera, so far as the vegetative portion is concerned, is that 

 a typical Compsonema, starting from a single cell, develops an exten- 

 sive, creeping, attaching mass of filaments, radiating in all directions 

 from the origin, which later produces very numerous erect filaments, 

 some of which remain sterile and others become fructiferous ; and 

 that a typical Ectocarpus, starting likewise from a single cell, develops 

 a rather insignificant series of attaching filaments, more or less 

 rhizoidal in nature, and a relatively extensive system of erect filaments 

 finally producing the fruit. Starting with this conception concerning 

 the two genera, we are assuming that diflt'erentiation has proceeded 

 from Compsonema in the direction of the reduction of the creeping 

 portion, to a more extensive development of the erect portion, finally 

 resulting in an Ectocarpus. 



