238 FRESH-WATER ALG^ OF THE UNITED STATES. 



CALOTHRIX MENEGHINIANA, Kirch. 



Forming strata on partially submerged rocks, usually 

 near the water line, composed of small, deep aeruginous or 

 brown dense tufts ; trichomes short, somewhat prostrate, at 

 first simple, later much and compactly branched. Cells 

 equal or half as long as wide. Sheath distinctly lamellose, 

 at the base yellow or brownish, at the ends colorless and torn 

 into fine fibers. Heterocysts usually single, same thickness 

 as the vegetative cells. 



Diameter of vegetative cells, 6-8 /x 

 Diameter of sheath, about 13 //. 



Syn. Schizosiphon MenegMnianus, Kg. 



Plate CLXX, figs. 5-7, three plants in different stages of 

 growth. 



CALOTHRIX RADIOSA, (Kg.) Kirch. 



Small tufts, sometimes gregariously extended on sub- 

 merged rocks, waving, made up of radiating, fasciculate 

 trichomes, about 40 // long, considerably branched ; stems 

 and branches somewhat curved, the two adhering about half 

 the length of the branches, ends free ; mostly of brownish 

 red color. Vegetative cells, i- i as long as wide. Sheath 

 close, golden yellow or colorless. Heterocysts single, glo- 

 bose, size the same as filament to which it is attached. 



Diameter of internal trichomes, 12 //. 

 Diameter of sheaths up to 30 // wide. 



Plate CLXX, figs. 1, 2, two plants drawn on a much smal- 

 ler scale than the others on the plate ; figs. 3, 4, a variety, 

 appears to stand between this species and C. Meneghiniana; 



figs. 8, 9, young forms of the last, (3, 4). 



CALOTHRIX BREBISSONII, Kg. 



Caespitose, bright aeruginous, or sometimes changing to 

 light brown, spurious branches short, stout, quickly atten- 

 uate to a hair-point, beautiful aeruginous ; distinctly and 

 shortly articulate, sometimes interrupted ; articles with 

 granular contents, 3-4 to diameter. Sheath usually close, 

 widens with age, colorless or light yellow. Heterocysts glob- 

 ular, single, at base of branches, colorless or light yellow. 



Diameter of trichomes, with sheath, 16-20-25 //. 



Submerged stones, ponds, New Jersey. 

 Plate CLXIX, figs. 5, 6, 7, two characteristic forms. 



