l6 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Calothrix Ag. (Mastigonema Schwabe; Mastigothrix 



Kiitz., in part). Filaments growing in tufts or soft masses, 

 rather rigid, straight and spuriously branched. The branches 

 are younger filaments glued at their bases and part of their 

 length to the parent stem ; the apex is delicately hair-like. 

 Heterocysts are normally present and are usually at the base 

 of the branches. 



[C. Braunii Born, and Flah. ; C. fusca (Kiitz.) Born, and 

 Flah. ; C. parte tina (Nag.) Thur.] 



Dichothrix Zanard. Filaments more or less dichotom- 

 ously branched ; several trichomes with their sheaths enclosed 

 within an outer common sheath. Heterocysts basal, or inter- 

 calary, or absent in one species. 



[D. gypsophila (Kiitz.) Born, and Flah.; D. Hosfordii 

 (Wolle) Born, and Flah.; D. Orisiniana (Kiitz.) Born, and 

 Flah.] 



Isactis Thur. The filaments are erect and parallel, at- 

 tached at the base. They are glued together by a more or less 

 firm mucilage, and are often encrusted with lime, forming flat 

 strata. 



Gloeotrichia J. Ag. The filaments, with spores in the 

 lower part, are radiate, sometimes spuriously branched, each 

 enclosed in a distinct, broad sheath, which is often furrowed 

 at the base and transversely folded. All the filaments are 

 enclosed in a more or less spherical jelly. 



G. Pisum (Ag.) Thur., Fig. 214. 



Rivularia (Roth.) Ag. (Zonotrichia J. Ag. ; Limnactis 

 Kiitz. ; Schizosiphon Kiitz., in part). 



Filaments radiating, with basal heterocysts, but no spores. 

 A more or less firm mucilage binds the filaments into a hemi- 

 spherical or bladder-like, well-defined thallus. One species of 

 Rivularia has been found in our studies, but no figure of it is 

 given in this report. 



FAMILY II. CAMPTOTRICHACE^. 



Not found in the United States. 



