THE GREEN ALGAE OF NORTH AMERICA 147 



the entering tube remaining as a cellulose thread with a knob- 

 like expansion at the surface of the host. In autumn the cell 

 may develop to a thick-walled akinete, producing gametes in 

 the spring. Fig. 33. N. H. Europe. 



2. C. KNYANUM Cohn and Szymanski in Kirchner, 1878, 

 p. 102 ; Klebs, 1881, p. 255, PI. Ill, figs. 11-15 ; P. B.-A., No. 

 1518. Cells of varying form but usually more or less elongate, 

 often with a distinct neck-like prolongation ; up to 100 /u, long ; 

 zoospores formed many in a cell, escaping through an opening 

 in the body of the cell, not in the neck-like prolongation, 

 enclosed in gelatinous vesicle, from which they soon escape 

 without copulation ; ovoid rather than pyriform, soon coming to 

 rest and penetrating the host plant ; thick-walled akinetes as in 

 C. Lemnae. Sexual reproduction unknown. In old fronds of 

 Ceratophyllum, Elodea, Lemna minor, L. gibba, etc., but never 

 found in L. trisnlca. Mass. Europe. 



As P. B.-A., No. 1517 was distributed an endophytic alga in 

 Sphagnum from Wood's Hole, Mass,, under the name of C. 

 Archcrianum Hieronymus, 1887, p. 296. The identification 

 must be considered doubtful, in view of the scanty description 

 given by the author of the species, and of some peculiarities of 

 the Wood's Hole plant, which may make even its generic posi- 

 tion uncertain. 



3. C. SCHMITZII Rosenvinge, 1893, P- 9 6 4. fig- 56. Cells 

 clavate or ovoid, with rounded apex and no papilla, and pointed 

 base; up to 370 p. long by 90 /u. diam.; chromatophore occupy- 

 ing the greater part of the cell wall, with two or more pyreuoids. 

 Endophytic in various crustaceous marine algae, Pctrocelis, 

 Cruoria, etc. Greenland to Me., Alaska to Washington. 



Northern Europe. 



4. C. DERMATOCOLAX Reinke, 1889, p. 88. Cells about 

 30X20 /j., seen from above rounded or oval, nearly plane below ; 

 external surface convex, subhemispherical or subconical ; asex- 

 ual reproduction by numerous zoospores, 4-6 //. long, escaping 

 by an opening in the end of the papilla formed at the apex of 

 the cell at the time of fructification. In Chactopteris pliiniosa, 

 Sphacdaria racemosa, etc. Greenland. Northern Europe. 



5. C. INCLUSUM Kjellman, 1883, p. 320, PI. XXXI, figs. 

 8-17 ; P. B.-A., No. 514. Cell globose or subglobose, or irreg- 

 ular by conditions of the host plant; usually 80-100 /A diam., 

 sometimes more than twice that size ; wall at first thin, later 

 thickening ; chromatophore covering the whole surface, with 

 many pyrenoids ; when fruiting a cone-shaped prolongation is 



