48 SPECIES OF ALG.E. 



b. Permanently attached, in rapid streams fluitans, 145 



b. Not permanently attached (c). 



c. Diameter of filaments 13-15.5;" ' . fontinali, 144 



c. " " " 25-33/1 stagnate, 145 



c. " " " 36-40;* Horsfordii, 145 



30. VAUCHERIA. 

 I. KEY TO THE STERILE PLANTS. 



In salt or brackish water; mats velvety, feet in extent, 



Thuretii, \ 49 



In sweet water or somewhat terrestrial (a). 

 Apparently terrestrial only (h). 



a. Filaments dichotomous, branches constricted at the base of the 

 divisions, often intermediately, tuberosa, 154 



a. Filaments not constricted at the branching points (b). 



b. Stratum dense, pellucid below, creeping; terminal branches erect, 



clustered, often crooked velutina, 153 



b. Stratum not pellucid below (c). 



c. Branches not clustered, vague. Thus far found only in California, 



hamata, 153 



c. Branches dichotomous or sparingly formed (d). 



d. Diameter of filaments ioo/* or more (<?). 



d. " " " less than ioo/* (g). 



e. Diameter 100 to 200/4 (/). 



/. Diameter 125/1; tufts dense, dark green .... geminata, 151 

 /. " ioo/i; tufts loose, expanding in all directions, 



aversa, 149 



f. " 100-200/1; dirty green or brownish; about limestone 

 springs dichotoma, 149 



/. Diameter 1 8o-2oo/*, often hyaline; drying ash gray . pilus, 153 



g. In turfy mats; filaments densely intricate; 50-75/1 in diameter, 



sericea, 150 



g. In dense, intricate tufts; filaments dichotomous, 50/1 in diameter, 



geminata, 151 

 *g. In loosely intricate clusters; filaments about 50^ in diameter, 



sessilts, 151 

 h. Stratum thin, expanded, filaments about 5o/f in diameter, 



Dillwynii) 150 



//. " " densely interwoven, dark green . . terrestris, 153 



