1 86 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



tween half tide and low water mark, for a long distance. It is 

 most abundant in winter and spring, but is found more or less 

 throughout the year. 



Several species have been segregated by Wille, 1901, from 

 U. flacca ; the new species are not at all easy to distinguish, 

 except when living ; probably all have passed as forms of 

 U. flacca in this country. The most certain marks of this 

 species are the always free filaments, with short cells, quite 

 occupied by the chromatophore, which is of nearly even thick- 

 ness throughout. 



n. U. SUBFLACCIDA Wille, 1901, p. 27, PI. Ill, figs. 90- 

 100 ; P. B.-A., No. 1275. Filaments 5-25 p. diam., attached by 

 a rounded basal cell ; cells 1-2 diam. long, rarely more or less ; 

 chromatophore a curved parietal disk, with one pyrenoid ; 

 zoospores formed 8 in a cell, broadly ovoid. 



Segregated from U. flacca by Wille, this species is to be rec- 

 ognized chiefly by the longer cells, with the chromatophore 

 quite thick at one side, where the pyrenoid is situated, thinner 

 in all directions, often not extending around the cell or to the 

 ends. The only locality with us is at California, where it was 

 found growing on a steamer whose daily route passed from fully 

 salt to fully fresh water. Such exceptional conditions would 

 naturally have their results on the plant, and it is of course 

 possible that under more normal conditions it would be different. 

 At present it answers well to Wille's species. 



12. U. laetevirens (Klitz.) nov. comb. ; Schizogonium laete- 

 virens Kutzing, 1845, p. 194; P. B.-A., No. 313. (?) U.conso- 

 ciata Wille, 1901, p. 25, PI. II, figs. 82-89. Filaments 10-25 p. 

 diam., two or three often firmly grown together laterally, more 

 or less entangled and creeping ; with not infrequent branches, 

 issuing at a wide angle, and usually much more slender than 

 the main filament, of many cells, which are generally 1-3 diam. 

 long ; filaments tapering towards the base, the lower cells of the 

 densely packed filaments often subparenchymatously united ; 

 cells y-Y\ diam. long, rarely more; chromatophore covering 

 nearly or quite all of the cell wall, but thicker at one side, 

 where the pyrenoid is situated ; zoospores usually 8 in a cell ; 

 akinetes formed singly from the cells. On woodwork between 

 tides. Canada, Me., Cal. Europe. 



The Canadian plant grew on alder logs at Cap a 1'Aigle ; the 

 material distributed as P. B.-A., No. 313, on fence rails be- 



