No. IO.] FRESH-WATER ALG.E. 29 



Cells irregularly grouped within a structureless 



mUCUS PALMELLE^E 



SUB-FAMILY I. GLCEOCYSTIDE/E. 



Plants formed of colonies of cells in a common mucila- 

 ginous envelope. Ordinarily concentric coats of mucus can 

 be seen around single cells or groups of cells. Multiplication 

 by division of the mother-cell into four parts. 



Key to Genera. 



Colonies irregular Glccocystis* 



Colonies cylindrical and branching (Palmodictyon 



Colonies subspherical Botrydina 



Description of Genera. 



Glceocystis Nag. (Chlorococcus Fries., in part). 

 Spherical or oblong cells associated in globose families of an 

 indefinite number of cells. Teguments gelatinous, formed in 

 layers. Cells spherical or ellipsoidal. 



G. vesiculosa Nag., Fig. 28. 



[G. rupestris (Lyng.) Rab.] 



Palmodictyon Kiitz. The cells and surrounding tegu- 

 ment are in the shape of cylindrical masses which branch and 

 anastomose. The outer covering is often hard and of a 

 reddish brown color. Reproduction by means of resting spores 

 with brown cell walls. 



Botrydina Breb. A genus little investigated. The 

 colonies are subspherical, made of cells enveloped in a thick, 

 gelatinous integument, which may be as large in diameter as 

 five hundred microns. 



SUB-FAMILY II. TETRASPORE/E. 



Cells grouped in fours or very irregularly scattered towards 

 the outside of a structureless mass of jelly. The cells of this 

 family are frequently provided with delicate non-vibratile hairs 

 called pseiidocilia. 



Description of Genera. 

 Tetraspora Ag. Thallus gelatinous, thick, at first baggy, 

 then lengthening; scattered through the jelly are numberless 



