19^0] SetchcU-Gardncr: MelanopJnjreae 437 



Growing- in minute tufts on the shells of Chitons and Limpets. 

 Pacific Grove and Carmel Bay, California. 



" Ectocarpus vkiionkolus" Saunders, Phyc, Mem., 1898, p. 150, 

 pi. 15, figs. 1-4. 



The illustrations of Saunders {Joe. cht.) show a diversity of forms 

 of the gametangia, ranging from long ones with many small loculi, to 

 short ones with few larg:e loculi. The species either possesses great 

 range of variation in this respect, or else there may possibly be two 

 species concerned. Another explanation of the phenomenon may be 

 the possibility that we have in this species the two forms of game- 

 tangia mentioned by Sauvageau (1896&, p. 17) found on Ectocarpus 

 viresccns. Saunders' figure 2 might well represent the "mega- 

 sporangia" and figures 3 and 4 the "meiosporangia" of Sauvageau. 

 The species needs further investigation to have the validity of these 

 points established. 



In the specimens we have examined, both that of Saunders and the 

 single one of Gardner's collecting, the gametang^ia are long, and 

 large-celled. The species is to be distinguished from any other of our 

 loAV forms by its discoid chromatophores and its peculiar habitat. 



30. Ectocarpus socialis S. and G. 



Plate 51, tigs. 12, 13 



Fronds eaespitose, 1-3 mm. high, attached by densely intertwined, 

 penetrating rhizoidal filaments; erect filaments several times forked 

 at the surface of the host, simple above or rarely alternately branched, 

 long-attenuate upwards, piliferous; cells cylindrical to slightly doli- 

 iform, not constricted, 22-28ju, diam., 1-2 times as long as the diameter 

 below, 4-6 times above ; chromatophores small, few in a cell, discoid ; 

 zoosporangia ellipsoidal, erect, lateral, alternate, mostly on 1-2-celled 

 pedicels, occasionally sessile near the base of the erect fronds, 60-95/x 

 long, 35-50/A broad ; gametangia fusiform, sparse on the upper parts of 

 the erect filaments; sessile or on 1-2-celled pedicels, alternate, 70-85ju. 

 long, 25-30/x broad. 



Growing on CacUiim fragile (Suring.) Hariot, in company with 

 Ectocarpus glohifer Kuetz. and with various species of Myxophyceae 

 and Rhodophyceae. Redondo, California. 



Setchell and Gardner, Phyc, Cont. VI, 1922, p. 412, pi. 46, figs. 

 12, 13. 



Ectocarpus socialis seems to be a relative of the E. c ijlindricws 

 group. The chief distinctions between the two species lie in the shape, 

 size and position of the gametangia. 



