THE GREEN ALGAE OF NORTH AMERICA 283 



and tortuous, the branches at right angles, forming a network 

 among the cells of the host ; short branches arising from the 

 cells of the network, the terminal cell of each branch develop- 

 ing into a sporangium at the surface of the host. Cells with 

 parietal chromatophore and one large pyrenoid. 



Evidently nearly related to Endophyton, but there is a sharper 

 differentiation between the two parts of the frond, the definite 

 horizontal network, and the short fruiting branches. The net- 

 work has a superficial resemblance to Microdidyon, but the re- 

 semblance is probably only superficial. 



P. GENICULATUM Gardner, 1909, p. 374, PI. XIV, figs. 5 and 

 6. Young cells 3-4 p. diam., becoming larger with age ; vertical 

 branches of 2-3 cells arising from practically all the cells of the 

 network ; sporangia 8-12 ^ diam. Fig. 120. In the cortical 

 layer of Laminaria Sinclaiiii, near San Francisco, Cal. 



The patent branches of the main filaments usually reach to a 

 neighboring filament, thus forming a network with subrec- 

 tangular meshes, each enclosing 4-8 cells of the host ; from this 

 network arise vertically short branches reaching to the surface 

 of the host and terminating in sporangia with rounded ends ; 

 the nature of the reproductive bodies formed in these sporangia 

 is not known. The plant is found chiefly in the terminal part 

 of the blade of the host. 



8. BOLBOCOLEON Pringsheim, 1862, p. i. 



Frond microscopic, epi- or endophytic in various algae ; fila- 

 ments creeping, branching, consisting of irregular rounded 

 cells, on the upper (outer) side of which are borne smaller bulb- 

 shaped cells, prolonged into a tube, from which projects a long, 

 slender hair ; ^chromatophore in the filament cells a parietal per- 

 forate layer with 5-10 pyrenoids ; in the piliferous cells an 

 irregularly toothed plate with two pyrenoids. Reproduction by 

 biciliate zoospores, produced in large numbers in the filament 

 cells ; whether sexual or asexual is not known. Only one 

 species. 



B. PILIFERUM Pringsheim, 1862, p. 8, PI. I ; Farlow, 1881, 

 p. 57 ; Hazen, 1902, p. 227 ; P. B.-A., No. 1225. Vegetative 

 cells 1 2- 1 6 /u, diam., 2-3 diam. long. Fig. 108. Newfoundland 

 to R. I.; California. Europe. 



Not uncommon in summer and autumn in various loose- 

 tissued marine algae, seldom in such quantity as to be noticeable 

 without microscopic examination, but occasionally occurring in 



