THE GREEN ALGAE OF NORTH AMERICA 349 



a well understood species, and perhaps it may some time prove 

 to be a winter form of something else. 



38. C. HOWEI Collins, 1909, p. 18, PI. LXXVIII, fig. i. 

 Forming dense matted tufts, consisting of creeping basal fila- 

 ments, with irregular cells about 150 //, diam., tapering to 75 ^ 

 at the growing tips, cells 1-3 diam. long; from these basal fila- 

 ments arise vertical filaments about 50 p. diam. at base, tapering 

 to 20-25 p. at the rounded or slightly pointed tip ; cells about 

 5-6 diam. long at the base, up to 15-20 diam. long near the tip ; 

 sparingly branched, branches erect or appressed, similar to the 

 erect filaments. Bermuda. 



Forming a dense coating in tide pools, about i cm. high ; the 

 base a mat of dark green, much branched, irregular fila- 

 ments, from which arise the slender, slightly branched, long- 

 jointed filaments, pale green under the microscope, yellow in 

 the mass. This yellow color may not be a permanent charac- 

 ter, as the same shade appears to be produced by local condi- 

 tions in some algae normally green. The contorted, densely 

 matted basal filaments indicate an affinity to the sub-genus 

 Aegagropila, but there is no indication of a definite form to the 

 whole mass. 



39. C. TRICHOTOMA (Ag.) Kiitzing, 1849, p. 414; 1854, PI. 

 LXIV, fig. i; P. B.-A., No. 820; C. repens, P. B.-A., No. 

 727, not of Harv.; C. columbiana Collins in Setchell and Gardner, 

 1903, p. 226. Forming light or bright green, densely pulvinate 

 masses, 2-5 cm. high ; filaments procumbent at base, stiff, di- 

 trichotomous with rather few short, alternate, rarely opposite 

 branches, fastigiate at the tips; cells 120-250/11 diam., 4-10 diam. 

 long, nearly cylindrical below, above ovoid to pyriform ; the 

 branches about the same diameter as the filament. Vancouver 

 Island to Southern Cal. Europe. 



In habit like C. repcns, but of lighter or brighter color and 

 larger cells. It grows in rock pools near high water mark, and 

 has been found from Vancouver to the Mexican boundary. It 

 seems impossible to draw any sharp line between C. trichotoma 

 and C. columbiana ; the form distributed as C. repens, P. B.-A., 

 No. 727, differs so much from the Mediterranean plant that it 

 seems best to include it under the present species. 



40. C. AMPHIBIA Collins, 1907, p. 200; P. B.-A., No. 1284. 

 Basal layer of densely branching prostrate filaments, cells cylin- 

 drical, 40-70 /A diam. and 2-5 diam. long, or fusiform, 1-2 diam. 



