150 STRUCTURAL BOTANY . 



daughter-cells grow. As the split takes place repeatedly 

 near the same place, a succession of caps is formed, one 

 corresponding to each cell-division. 



We thus see that the vegetative structure of an 

 CEdogonium is excessively simple far simpler than that 

 of any plant which we have hitherto described. We 

 have now to consider the way in which the Alga 

 reproduces itself. 



There are two distinct methods, the one asexual, the 

 other sexual. The former serves to propagate the plant 

 rapidly during summer, or as long as the conditions are 

 favourable to its growth ; the latter has for its result 

 the production of resting -spores, which can survive alike 

 the cold of winter and the periods of drought to which 

 CEdogonium, in common with other fresh-water Algre, is 

 often exposed. 



2. EEPRODUCTION 



a. Asexual 



Any vegetative cell may serve as an organ of asexual 

 reproduction, and many individual plants only show this 

 mode of propagation. 



The entire contents of a cell are used up to form a 

 single spore. The protoplasm gradually withdraws itself 

 from the cell-wall, the whole mass assuming a rounded 

 form. At the same time a clear, colourless spot appears 

 on one side of the contracted protoplasmic body. From 

 this clear portion of the protoplasm numerous cilia are 

 developed. The cell-wall splits across and the crack 

 opens widely at one side, that, namely, towards which 

 the clear patch of protoplasm is turned. The spore now 

 begins to pass out through the opening, changing its form 



