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



Conjugation producing a zygospore which immedi- 

 ately develops a sporocarp of several cells, one of 

 which is the spore. The gametophyte is developed 

 from this spore after a period of rest. . . . mesocarpe^e 



SUB-FAMILY I. ZYGNEME,E. 



Filaments unbranched. A lining of protoplasm is in each 

 cell, and the nucleus is held in the centre by quite prominent 

 bands of protoplasm. The chloroplasts containing numerous 

 prominent pyrenoids are twin stellate bodies in Zygnema and 

 spiral bands in Spirogyra. 



Vegetative multiplication by breaking of filaments into 

 separate cells or groups of cells. Asexual reproduction 

 by spores. Sexual reproduction by conjugation between 

 cells of different filaments which lie close together. Each 

 cell puts out a tube on the side nearest the other fila- 

 ment, and these meet with similar tubes from the cells 

 of the other filament. The ends of the tubes join, and an 

 open " conjugating tube " is formed. The contents of the 

 cells separate from the cell walls, and the mass from one cell 

 flows into the other, there to unite with the mass in that cell 

 and form a zygospore. The zygospores are usually all found 

 in one of the two filaments. Occasionally lateral conjugation 

 between two cells of the same filament is observed. 



Key to Genera. 



Cells containing two star-shaped chlorophyll bodies 



near the nucleus Zygnema'* 



Cells with spirally twisted bands of chlorophyll. . . 



Spirogyra* 

 Cells with nearly straight bands of chlorophyll. Choaspis* 



Description of Genera. 



Zygnema Ag. (Zygogonium Kiitz.). Cells with two 

 star-shaped chlorophyll bodies near the nucleus, each chloro- 

 plast bearing a starch grain. 



Z. leiospermum D. By., Fig. 176. 



Z. stellium Ag., Figs. 177, 178. 



Z. stellium var. genuinum Kirch., Fig. 179. 



