ZOOSPORES 



217 



hinges back to form an aperture through which the contents 

 slowly ghde (c). At the moment of hberation the almost spherical 

 zoospore is surrounded by a thin bladder of extruded mucilage (d), 

 but it almost immediately commences to move away with the 

 help of its cilia, though rather more slowly than in the case of 

 Ulothrix or Cladophora. Sooner or later the zoospore becomes 

 attached to some submerged object by its colourless front end 



Fig. 117. — (Edogonium. a, single cell, highly magnified (after Schmitz), 

 showing the net-like chloroplast with pyrenoids {p.), and 

 the single nucleus {".) : b-g, (Edogonium concaienatum (after Hirn) ; 

 b-d, stages in formation of zoospores ; e, liberation of ditto ; / and g, 

 germination of zoospores (in g the characteristic attaching cell is 

 seen) ; h, CEdogonimn pachyandrium (after Hirn), showing cells with 

 caps (c), and an oogonium [oog.). 



(Fig. 117, /), and the cilia are withdrawn ; then a cell-wall 

 is secreted and division takes place to form a new filament, 

 whilst the end in contact with the substratum grows out into 

 the branched holdfast (Fig. 117, g). 



In the case of Vaiicheria, zoospore-production commences 

 with the swelling of the tips of the branches, which become 

 filled with abundant cytoplasm, chloroplasts, etc., and are finally 



