26 GENERA OF ALG^E. 



B. Axillary thread a single series of cells with transverse threads at 



regular intervals Lemanea, i 



C. Axillary thread of cohering filaments, with many whorls of mon- 



iliform branchlets Tuomeya, 2 



D. Simple or branched, slippery; cells in a single layer, membrane 



thick, colorless Bangia, 3 



E. Branched; main stem often with an external, parallel series of 



cells; branches moniliform, clustered . . Batrachospermum, 4 



E. Branched; main stem without external parallel series of cells; 



branches not moniliform (F). 



F. Filaments articulate, villose, branchlets dichotomous . Thorea, 5 

 F. Filaments articulate; branches not whorled; plant steel blue or 



purplish Chantransia, 6 



F. Filaments articulate; branches erect-spreading; plant olive-green, 



Compsopogon^ 8 



CLASS II. 



Multicellular or apparently so (A). 



Unicellular, the cells often clustered or forming a colony (F). 



A. Chlorophyll diffused, not in patterns (B). 



A. Chlorophyll in spiral bands, axillary laminae, or twin, stellate 



nuclei (/>). 



B. Filamentous (C). 



B. Not filamentous; articulate, prostrate, or net-like, often membra- 



nous, sometimes parasitic (M). 



C. Basal cell lobately divided, or with a terminal disk attaching the 



young plant (D). 



C. Basal cell not lobate nor disciform (E). 



D. Not branched; terminal cell sometimes setiform, (Edogonium, 10 

 D. Not branched; no setae; strongly contracted at intervals, 



Schizomcris, 243, 

 D. Branched; with long terminal setae bulbous at base, Bulbochate^ u 



D. Branched; no setae; cells long, cylindrical . . . Sciadium, 46 



E. With branches (G). 



E. Without branches, but sometimes with lateral processes (L). 



F. Plants filamentous (N). 



F. Plants not filamentous, sometimes curved or spiral, without root- 

 lets (T). 



F. Plants globose, small, on moist earth, with colorless rootlets (O). 



G. Filaments erect (H). 



G. Filaments prostrate or creeping, branched or not (*). 



