GENERA OF ALG/E. 33 



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

 less, not in families . . Hy drums, 52 



d. Tegument mucous, with small indistinct families of innumerable 

 cells . . . . . ... . . Anacystts, 117 



d. Tegument soft, thick . . . . Aphanocapsa, 120 



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

 surrounded by another tegument . . . Glceocapsa, 119 



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



small, on the surface . ... Ccelosphmrium, 113 



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



Aphanothece, 110 

 c. Tegjument inconspicuous; cells elongate, cylindrical, 



Synechococcus, i ii 

 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, Chrookpus, 22 

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



Asterothrix, io6a 

 g. Somewhat dichotomously branched, apices rounded; floating and 

 yellow, or 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 . Glaotrichia, 84 

 h. Filaments agglutinated by mucilage, and forming hemispherical or 

 bladdery forms . . .....*.. Rivularia, 85 



