36 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



four are held together by a tough mucilage. Multiplication by 

 autocolonies. The only American genus is the following: 



Crucigenia Morren (Staurogenia Kiitz. ; Lemmer- 

 mannia Chodat; Willea Schmidle). 4, 8, 16, or 32 sub- 

 quadratic cells, gathered into a flat ccenobium held in a mucila- 

 ginous envelope. As many as 128 cells in groups of four have 

 been discovered. The cell walls are smooth, and each cell is 

 furnished with a single chloroplast. Multiplication by auto- 

 colonies. 



SUB-FAMILY VI. PHYTHELIE^E. 



Unicellular or grouped in a more or less definite ccenobium, 

 freely floating. Almost devoid of a mucous envelope and fur- 

 nished with bristles. 



SUB-FAMILY VII. CCELASTRE.E. 



The cells are either globose or polygonal, provided with 

 processes by which they are united into a hollow sphere ; or 

 broadly lunate, and united at the centre by short stalks. 

 Propagation by autocolonies which are formed in each cell of 

 the ccenobium. 



Key to Genera. 



Ccenobium hollow Coclastrum* 



Ccenobium solid So rostrum* 



Description of Genera. 



Ccelastrum Nag. (Hariotina Dang.). Ccenobium a 

 hollow globe formed of a single layer of green, spherical or 

 angular cells ; later the ccenobium appears to be reticulately 

 pierced ; in older growths the cells have become polygonal 

 through continued pressure. Daughter-ccenobia are developed 

 within the mother-cell, and escape by breaking the walls of the 

 latter. Found in ponds. 



C. micro porum Nag., Fig. 51. 



Sorastrum Kiitz. (Selenosphaerium Colin). Differs 

 from Ccelastrum in that the ccenobium is solid. It is composed 

 of 4, 8, 16, or 32 wedge-shaped stalked cells, radially disposed, 

 with spines (usually two) on each end. Propagation by auto- 

 colonies. 



