326 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



The most slender erect marine species known, not likely to 

 be mistaken for an} r other. 



8. C. CHELONUM Collins, 1907, p. 198. Filaments erect, 

 straight, 12-20 fj. diam. at the base, increasing to 35 /u, diam. 

 above; lower cell up to 50 diam. long, following cells 5-10 

 diam., upper cells 2-3 diam.; wall thick ; attached by coralloid, 

 pluricellular branches ; fertile upper cells moniliform to globu- 

 lar, up to 50 fi diam., i-4-diam. long. Mich. 



The only fresh water Chactoinorpha known in America, and 

 distinguished from all other species, fresh water or marine, by 

 the pluricellular branches issuing from the base of the filament, 

 which may form a dense, inextricable mass on the substratum, 

 which in the original and so far only known station was the 

 backs of living turtles. 



Doubtful species. 



C, saccata Kiitzing, 1849, p. 380. 



C, intestinalis Kiitzing, 1849, p. 380. 



C. media Kiitzing, 1849, p. 380. 



C. tcnuissima Crouan in Maze and Schramm, 1870-77, p. 51. 



2. RHIZOCLONIUM Kiitzing, 1843, p. 261. 



Filaments usually prostrate, of a single series of multinucle- 

 ate cells, with net-shaped chromatophore and several pyrenoids, 

 unbranched or in some species wdth a few irregular branches 

 similar to the axis, and with more or less numerous rhizoidal 

 branches, mostly unicellular, but sometimes of several cells. 

 Asexual reproduction by biciliate zoospores with stigma, escap- 

 ing through an opening in the cell wall ; also by akinetes ; but 

 in only a few species has either form of fructification been 

 found. 



Common plants of fresh and salt water, often forming exten- 

 sive mats in shallow 7 water or on ground in the literal zone ; the 

 filaments resembling those of Chaetomorpha, but less uniformly 

 cylindrical, there being almost always more or less irregularity 

 in the form of the cells. The short rhizoidal branches, when 

 present, clearly characterize the genus, but they are not always 

 developed, and when they are absent, the resemblance to Chaeto- 

 morpha is deceptive. In the few species where there are 

 branches other than rhizoidal, they are formed quite differently 

 from those of Cladophora, the branch pushing the original fila- 

 ment out of place, itself continuing in the original direction. 



