THE GREEN ALGAE OF NORTH AMERICA 361 



Often confused with .5*. arcta, which in its older stages is 

 much matted ; but in that species the filaments are united by 

 the descending rhizoidal branches only ; in 6". spinesccns chiefly 

 by the hooked branches. 



7. S. coalita (Rupr.) nov. comb. ; Cladophora coalita P. 

 B.-A., No. 819; C. scopacformis Harvey, 1858, p. 75 ; P. B.-A., 

 No. 922. Fronds at first loosely tufted, but soon forming dense, 

 rope-like branching tufts, up to 30 cm. long ; at first bright, 

 later dull or yellowish-green ; filaments 100-250 ^ diam. in the 

 terminal cell ; branching dichotomous below, irregularly alter- 

 nate above ; all branches of this class erect, with blunt or trun- 

 cate ends ; also present, except in very young plants, abundant 

 patent, tapering, very acute, hooked or circinate branches, by 

 which all the older parts are densely matted together ; cells y$-i 

 diam. long in the lower part of older plants, 2-3 diam. in 

 younger plants, and even 6-10 diam. in the active terminal cell. 

 Alaska to Cal. Kamtschatka. 



The hooked branches distinguish this species from all others 

 except S. spinescens, which is a smaller plant, with filaments 

 about half the size of those in .S. coalita. In the review of this 

 group in Setchell and Gardner, 1903, p. 227, Cladophora coalita 

 and C. scopacformis were considered distinct species, but on look- 

 ing over material from various points, and collected at various 

 seasons, it seems impossible to keep them separate. C. polaris 

 Harvey would seem to be the very young plant, with normal 

 erect branches only, and with texture delicate. When the 

 plant has nearly reached its full growth, it is C. scopaeforuiis, 

 with long, green, actively dividing terminal cell to each normal 

 branch ; in the lower part of the filaments the cells are consid- 

 erably shorter, and the walls cartilaginous ; hooked branches 

 are plentiful. At a still later stage the terminal cells have 

 ceased to grow at the tip as fast as new cells have been cut off 

 below ; they are but little distinct from the other cells, either in 

 length or texture. The division of the lower cells has gone on 

 until most of them are shorter than their breadth ; hooked 

 branches have been developed until the greater part of the 

 plant is now shaggy with them. The plant is now typical 

 Conferva coalita of Ruprecht. C. cartilaginca Ruprecht very 

 likely should be here included; btit the description, 1856, p. 

 404, is hardly sufficient, and no authentic specimens are ac- 



