OEDOGONIALES 



59 



division is unique, and although there is no trace of its ancestry 

 its constancy suggests that the group terminates a line of 

 evolutionary development. Vegetative reproduction commonly 

 occurs by means of fragmentation, whilst asexual reproduction is 



Fig. 43. Oedogonium. A, idioandrosporous nannandrous filament. B, g>'nandro- 

 sporous nannandrous filament. C, dioecious macrandrous filament. D, monoe- 

 cious filament. E-H, stages in development of dwarf male plant ( x 400). 

 I, antherozoid ( x 480). J, escape of zoospore (X138). (A-D, after Mainx; 

 E-I, after Ohashi; J, after West.) 



secured through akinetes or multiflagellate zoospores, the forma- 

 tion of the latter being said to depend on the presence of free 

 carbon dioxide in the water. The flagellae, which may have one or 

 two rings of granular blepharoplasts at their base, form a circular 

 ring around an anteriorly situated beak-like structure. This is the 

 typical oedogonian swarmer, one of which is produced by each cell, 



