1^-5] Setchell-Gardner: Melanophyceae 405 



nec'ted ; zoosporangia formed simultaneously, 7-12 catenate, mostly 

 terminal in the ramuli, spheroidal, 24-28/x diam. ; gametangia unknown. 



Growing on rocks in shallow pools near high-tide limit. Sunset 

 Beach, near the mouth of Coos Bay, Oregon. 



Setchell and Gardner, Phyc. Cont. V, 1922, p. 386, pi. 42, figs. 6-8. 



The secund branching together with the longitudinal divisions of 

 the cells from Avhich the secund branches arise, forming a polysiphon- 

 ous region, are the chief distinguishing characteristics of this species. 

 The branching below is sparse, alternate or very rarely opposite, and 

 the branches are relatively long and attenuated. These branches may 

 give rise to terminal zoosporangia, or to a few short alternate ramuli 

 which in turn produce the zoosporangia. Many of the main filaments 

 become slightly enlarged towards their outer ends, the cells becoming 

 nearly quadrate, their walls thickened and their contents very dense. 

 An average of about thirty-five, although frequently as many as sixty- 

 five, cells are thus transformed. A few cells of the ends of the fila- 

 ments are not transformed and soon disintegrate, thus producing 

 decidedly clavate filaments. The region of transformation seems to 

 be a new meristem of a peculiar nature. Many of the cells divide 

 once or, less frequently, twice, by longitudinal planes as a rule, but 

 occasionally the dividing planes are at right angles separating the 

 cell into four parts. The unique feature resulting from these divi- 

 sions is the lack of further growth of the cells. Usually one of the 

 cells resulting from longitudinal division gives rise to a branch, 

 shorter or longer, but similar to branches arising in the regular man- 

 ner. The branches are typically secund, but may rarely come from 

 the opposite side of the filament. Many of the main filaments become 

 much curved in this branching region. 



3. Pylaiella Gardner! Collins 



Erect assimilating filaments slightly attenuated when young, 

 unbranched or sparsely forked near the base giving rise above to 

 numerous, short, obtuse, mostly opposite, rigid, patent branches, 

 10-12 mm. (up to 20 mm.) high; cells at base of filaments 12-15/x 

 diam., twice as long as broad, increasing in diameter slightly upwards, 

 moderately constricted at the joints; creeping filaments 6-10|a diam., 

 cells 1-4 long; chromatophores thick, broken bands nearly filling 

 the cell ; zoosporangia unknown ; gametangia in terminal, more or less 

 clavate, series, either on the main filaments or on short lateral branches, 

 up to 24/i, diam. 



