No. IO.] FRESH- WATER ALG.E. 47 



Description of Genera. 



Microthamnion Nag. Filaments articulate, variously 

 branched, straight; end cell at first linear, then obtuse, and 

 finally swollen into a sporangium. The plants are at first fixed, 

 but later free-floating. The branches arise just below a trans- 

 verse cell wall. The chloroplast is parietal, long and entire, and 

 lacks a pyrenoid. 



This genus is frequently placed with the Trentepohliacece ; 

 but Hazen states that the zoogonidia may be produced in any 

 cell of the filament, and hence it has its relationship near 

 Myxonema. Two species are found in Connecticut, according 

 to Hazen. 



[M. Kuetzingianum Nag. ; M. strictissimum Rab.] 



Myxonema Fries (Stigeoclonium Kiitz.). Filamentous, 

 simple, branched, articulate ; the branches not in tufts, in ap- 

 pearance much like the main stem, with the end cells often 

 drawn out into long, colorless bristles. The chloroplasts are 

 scattered or arranged as in Drapamaldia. One to many zoogo- 

 nidia, each with two or four vibrating cilia, formed from the 

 contents of one cell. Gametes with 4 cilia. Zygospores smooth 

 or stellate. 



M. attenuatum Haz., Fig. 220. 



.1/. tenue (Ag.) Rab., Figs. 79, 82. 



M. nanum (Dillw.) Haz., Fig. 284. 



M. lubricum var. varians Haz., Fig. 81. 



M. sp. (?), Fig. 78. 



[M. Hagelliferum (Kiitz.) Rab.] 



Chaetophora Schrank. Plants enveloped in a hard, gela- 

 tinous covering of a globose, plane or lobed form. Thallus 

 filamentous, articulated and branched. Stems radiately dis- 

 posed, dividing into short branchlets, sometimes ending in a 

 bristle. The zoogonidia have two or four cilia, and resting 

 spores are generally developed from terminal cells and are 

 brown. 



C. incrassata (Huds.) Haz., Fig. 221. 



C. pisiformis (Roth) Ag., Fig. 222. 



[C. attenuata Haz.] 



Drapamaldia Ag. Filaments articulate, much branched. 

 The stem is thick and composed of sterile cells, colorless 



