GENERA OF ALGJE. 33 



d. Tegument mucous, cells spherical or elongated, one pole color- 

 less, not in families Hydrurus, 52 



d. Tegument mucous, with small indistinct families of innumerable 



cells Anacystis, 117 



Tegument soft, thick Aphanocapsa, 120 



Tegument a mucous stratum, containing groups of two cells, these 

 surrounded by another tegument Glozocapsa, 119 



d. Tegument a mucous stratum; thallus spherical, hollow, cells many, 



small, on the surface Cadospharium^ 113 



e. Tegument confluent, firm; cells longer than broad, 



Aphanothecg) 1 1 o 

 e. Tegument inconspicuous; cells elongate, cylindrical, 



Synechococcus, 1 1 1 

 e. Tegument soon perforate, breaking into lobed forms; cells very 



small, embedded Clathrocystis, 118 



/. Cells globose, united in families, clustered grape-like, 



Polycystis, 118 



g. Irregularly branched, often closely interwoven; stems and pri- 

 mary branches -of the same thickness; often aerial, Chroolepus, 22 

 g. Cruciformly branched, ends acute; filaments articulate or not, 



Aster othrix, io6a 



g. Somewhat dichotomously branched, apices rounded; floating and 



yellow, o,r not yellow and coating wet rocks . . Calothrix, 81 



h. Filaments erect, laterally adherent, basally attached, forming layers 



on flat surfaces Isactis, 83 



h. Filaments distinctly sheathed at base, sheaths broad, often sac- 

 cate, transversely plicate; heterocysts basal . . Glcurtrickia, 84 

 h. Filaments agglutinated by mucilage, and forming hemispherical or 

 bladdery forms Rivularia, 85 



