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



branches loose and spreading, except sometimes at the tips ; 

 ramuli short-pointed or setiferous ; cells in main filaments 6-u, 

 usually 8 /* diam., 3-10 diam. long; in ramuli 5-7 /* diam., 1-4 

 diam. long. Fig. 85. Mass, to N. J., Jamaica, Washington. 



Europe. 



Ranging in size from hardly visible spheres to tuberculose and 

 confluent forms, over i cm. diam. ; mostly in spring, but occa- 

 sionally at any time except when* the brooks are frozen. In 

 general character much like the two following species, but 

 generally of lighter color, softer texture, and less regularly 

 spherical shape. 



2. C. PISIFORMIS (Roth) Agardh, 1812, p. 43 ; Harvey, 1858, 

 p. 70; Wolle, 1887, p. 116, PL CIII, figs. 1-3, 12-15; Hazen, 

 1902, p. 212, PL XXXVIII, fig. i. Thalli globose or tubercu- 

 lose, 2-5 mm. diam., rather dark green, firm, seldom confluent ; 

 filaments radiating from the center, dichotomously, rarely tri- 

 chotomously branched, branches erect or appressed, ramuli 

 slender, acute, sometimes setiferous ; cells in main filaments 

 usually 6-7 p. diam., sometimes slightly more or less, 3-6 diam. 

 long; in ramuli 4-6 p diam., 1-3 diam. long. Me. to N. J., 

 Washington. Europe. 



The habit characters by which this differs from C. elegans are 

 given under the latter species ; microscopically, C. pisiformis has 

 more slender filaments and more erect branching. The charac- 

 ter of presence or absence of setae, formerly supposed to be of 

 specific importance, is now known to be of no value, varying 

 with age and circumstances. This species is especially a plant 

 of running water. 



3. C. ATTENUATA Hazen, 1902, p. 213, PL XXXIX; P. 

 B.-A., No. 1520. Thalli globose or nearly so, not confluent, 

 2-5 mm. diam., bright green, dense and firm ; filaments di- 

 trichotomously branched, very erect and nearly parallel, not 

 fasciculate ; ramuli acute or setiferous ; cells of main filaments 

 5-5.5 p. diam., 5-10 diam. long ; of the ramuli about 4 ^, rather 

 longer in proportion ; branch-bearing cells often broadened and 

 forked at the top ; descending rhizoids abundant in the lower 

 part of the frond. Mass., Conn., N. J. 



In habit quite like C. ptsiformu, but distinguished by more 

 slender filaments, very regular branching, ramuli long and 

 rather distant, rhizoids abundant. A plant of quiet water, and 

 of summer rather than of spring. 



4. C. INCRASSATA (Huds.) Hazen, 1902, p. 214, PL 



