Chloroplast a parietal plate covering most of the cell wall, with 1 



pyrenoid. Heterogamous in sexual reproduction, in which are formed 



enlarged oogonia, each containing a single egg, and box-like 



antheridial cells, each producing a single biflagellate antherozoid. 



Monoecious or dioecious. The oogonium becomes invested by a 



proliferation of neighboring vegetative cells after fertilization of 



the egg. 



Key to the Species 



1. Thallus composed of irregulariy branched filaments of rectangular cells 

 growing within the walls of Nitella and Chara.- „ C. Nitellarum 



1. Thallus not endophytic in the walls of Nitella and Chara 2 



2. Thallus a prostrate disc or horizontal expanse 



of regular or irregular outline 3 



2. Thallus a cushion of both prostrate and 



erect branching filaments 6 



3. Thalhis a series of spreading, branched filaments 



which are not laterally adjoined 4 



3. Thallus a horizontal, continuous disc with the filaments laterally 



adjoined and sometimes scarcely evident 5 



4. Branches not adjoined laterally, radiating 



from a common center .._ C. soluta 



4. Branches not adjoined, not radiating, but spreading 



and branching irregularly C. irregularis 



5. Cells large, up to 46At in diameter; thallus a horizontal 



disc with irregular outline C. scutata 



5. Cells smaller, 12-15/x in diameter; thallus a horizontal 



disc with a regular outline C. orbicularis 



6. Thallus a cushion-like mass of irregularly 



branching filaments — C. diver gens 



6. Thallus a cushion-like mass of regularly branching filaments 



radiating from a common center C pulvinata 



Coleochaete divergens Pringsheim 1860, p. 5 

 PI. 17, Figs. 5-7 



Thallus composed of irregularly branching filaments which do 

 not radiate from a common center but spread irregularly, forming 

 a cushion of upwardly directed fronds in which many of the cells 

 are setae-bearing. Cells 25-30-(35)ja in diameter, 30-125/x long. 

 Thalli monoecious. Oogonia (including cortex) 130-140/x in diameter. 



This species should be compared with C. pulvinata, which also 

 forms cushion-like thalli. C. divergens lacks the definite radiate 

 arrangement of the branches that characterizes C. pulvinata. The 

 vegetative cells of C pulvinata average slightly larger than those 

 of C divergens. 



Epiphytic on Nitella and other submerged aquatics, or on decay- 

 ing fragments of vegetation, culms of rushes, etc. Mich., Wis. 



[128] 



