174 



PHYLUM II. CHLOROPHYCEAE 



Fio. 68. 

 Oedogonium, 



producing 4-ciliate zoospores, or 2-ciliate gametes. The 

 irregularly tubular Enteromorphas resemble the Sea 

 Lettuces and are common in brackish ponds. 



245. In the Oedogoniums (Oedogoniaceae) the plants 

 are attached below, and are simple or branched above. 

 They propagate by means of multiciliated zoospores which 

 are formed singly in the cells, and generate by hetero- 

 gametes, consisting of small multiciliated sperms, and 



large non-ciliated eggs. The sperms are 

 formed (1) in certain cells in the filament 

 which produces the eggs, or (2) in some- 

 what smaller filaments, or (3) in very 

 small, few-celled filaments ("dwarf males")- 

 The eggs are formed singly in oogones that 

 are merely transformed and considerably 

 enlarged vegetative cells. When the egg 

 reaches maturity the oogone wall opens to admit the 

 sperm, after which the egg becomes a thick-walled rest- 

 ing spore. In germination the resting, spore divides into 

 four multiciliated zoospores which soon come to rest and 

 develop into ordinary vegetative filaments. 



246. The little Disk Algae {Coleochaetaceae) are minute 

 branching plants closely related to the Oedogoniums, 

 whose radiating filaments usually fuse later- 

 ally into small disks or cushions, a milli- 

 meter or so in diameter, and occurring on 

 the stems and leaves of larger water plants. 

 They propagate by biciliated zoospores 

 formed singly in the cells, and generate by 

 heterogametes. The biciliated sperms are 

 formed singly in the antheridial cells. 

 The oogones are terminal and each contains 



a single egg, and is supplied with a tubular prolongation, 

 the "trichogyne." 



