284 University of California PiiUications in Botany [Vol. 8 



Wille (1901, p. 22) has raised the question as to the exact nature 

 of the type of this species and as to the status of other plants referred 

 to it. Hazen (1902, p. 155) thinks, however, that Wille 's doubts are 

 not founded on sufficient basis for rejecting the name and that the 

 type of U. implexa may be reckoned among the marine species. 



We have followed the usual fashion of referring here our most 

 slender species whose cells are usually as long as, or often longer than, 

 broad. The chromatophore in young cells in active vegetative con- 

 dition forms a more or less complete band about the middle of the 

 outer cell wall. Many of our specimens, however, seem to have a 

 complete chromatophore clothing the entire outer wall. We are 

 inclined to consider the cells of such specimens as probably passing 

 over into the fertile condition, but not, as yet, having undergone divi- 

 sion to form zoospores or gametes. The fertile cells in these species 

 are neither enlarged (i.e., broadened) nor swollen. A careful study 

 of living material in various stages will be very helpful in clearing 

 up these matters. 



We follow Hazen in placing the Ulothrix suhfiaccida Wille Hoc. 

 cit.) as a synonym under U. implexa. 



2. Ulothrix flacca (Dillw.) Thur. 



Plants forming bright or dark green, often much entangled, masses 

 or skeins; cells 10-25/a diam., 0.25-0.75 as long as broad, when pro- 

 ducing spores up to 50/x diam., and swollen in the middle; chromato- 

 phore occupying the whole of the cell wall with 1 to 3, occasionally 

 more, pyrenoids. 



Growing on other algae, on rocks and on wood, in the littoral belt. 

 From Alaska to California. 



Thuret, in Le Jolis, Liste Alg. Mar., 1863, p. 56; Collins, Green 

 Alg. N. A., 1909, p. 185 ; Saunders, Alg. Harriman Exp., 1901, p. 412 ; 

 Setchell and Gardner, Alg. N.W. Amer., 1903, p. 217 ; Hazen, Uloth. 

 and Chaetoph. U. S., 1902, pi. 20, f. 7-9. Conferva flacca Dillw., 

 Brit. Conf., 1809, pi. 49. 



We can not feel certain whether the Ulothrix flacca, as it has been 

 finally limited by Wille (1901, p. 18 et seq.) is the Conferva flacca of 

 Dillwyn (loc^cit.) or not. There is a certain strong suggestion to 

 our minds of Ulothrix pseudoflacca Wille in both the figures and the 

 description of Dillwj'n. It seems best, however, to follow the present 

 conception of the species and assign under U. flacca marine Ulotriches 



