19-i^] ISetchell-Gardncr: Melanophyccae 469 



18. Myrionema phyllophilum S. and G. 



Fronds forming cushions more or less circular in outline, 400-800/a 

 diam. ; creeping portion composed of straight filaments radiating from 

 the center, closely crowded ; erect filaments unbranched, cylindrical, 

 constricted at the base, llO-lSOfi long, attenuated upwards, piliferous 

 in part ; true hairs scattered promiscuously among the erect filaments 

 and gametangia; cells of creeping filaments cylindrical, 4-5|U diam., 

 2-4 times as long; cells of erect filaments 8-9/i, diam., quadrate, to 2.5 

 times as long ; cells of the hairs quadrate at the base, 5-6fi diam., up 

 to 20 times as long in the upper part ; zoosporangia ( ?) broadly clavate, 

 sessile or terminal on longer or shorter pedicels, 50-70ju. long, 14-18;u, 

 broad at the outer end ; gametangia cylindrical, mostly on 1-2-celled 

 pedicels, on the creeping filaments, or more rarely lateral on the base 

 of the erect filaments, lilunt, 90-130/x long, 9-11/a broad ; loculi 

 uniseriate. 



Growing on the outer ends of the blades of eel-grass, in the lower 

 littoral and upper sublittoral belts. Sitka, Alaska. 



Setchell and Gardner, Phyc. Cont.- II, 1922, p. 344, pi. 32, figs. 1-5. 



In this species about one-third of the erect filaments remain sterile, 

 and extend beyond the gametangia. The cells in the creeping filaments 

 are relatively long. The filaments are closely crowded, but distinct 

 and readily separable. All the erect filaments are abruptly narrowed 

 at the base. On account of the long creeping cells, the erect filaments 

 are very much less crowded than is usually the case in most Myrio- 

 nemas. The erect filaments do not arise successively toward the margin 

 of the nearly mature plants, cells here and there developing an erect 

 filament to the length of several cells before the intervening cells show 

 signs of farther growth. The gametangia are typical of the genus, 

 with uniseriate loculi and with mostly horizontal, cross cell walls. The 

 zoosporangia (?) are fairly abundant, and are either with the game- 

 tangia on the same individual or on separate individuals. We ques- 

 tion these structures as being functional since none of them has been 

 observed to produce zoospores. They have the appearance of being 

 abortive organs, either zoosporangia or gametangia, more likely the 

 latter, and are probably like the organs observed by Magnus which 

 induced him to establish the genus Ascocyclus. 



