122 PLANT LIFE. 



A second and more complicated formation of antherozoids 

 takes place as follows. Asexually-formed zoospores called 

 androspores, closely resembling the antherozoids already de- 

 scribed in form and size, are produced in special short cells 

 of a filament. On their escape they attach themselves to the 

 filament on or near an oogonium, and develop into very 

 small male plants, called "dwarf males,'' consisting of two 

 or three superposed cells, the terminal one becoming an 

 antheridium, in which are formed two or three antherozoids, 

 that escape by the separation of the upper portion of the 

 wall of the mother-cell in a circumscissile manner. 



The oogonia are produced on the same plants as the 

 antheridia or on different ones, depending on whether the 

 species is monoecious or dioecious. They are always de- 

 veloped in cap-cells, and may be solitary or in groups. The 

 oogonia become swollen into an elliptical or spherical form, 

 and the protoplasm contracts into an oosphere, having its 

 chlorophyll grains massed together at one part, leaving a 

 colourless " receptive spot," opposite to which the wall of 

 the oogonium opens in a definite manner. Through the 

 opening thus formed, a mucilaginous substance protrudes, 

 to which the antherozoids become attached, and thus reach 

 the receptive spot. After fertilization the oosphere be- 

 comes clothed with a thick cell-wall, changes to a brown 

 colour, and becomes a resting-spore, still remaining within 

 the oogonium, which breaks away from the filament. 



On germination, the contents of the resling-spore breaks 

 up into zoospores, each of which gives origin to several 

 generations of asexual plants produced by zoospores, after 

 which plants with sexual organs are produced. 



The species of Bulbochate are closely allied to (Edogonium 

 in the sexual mode of reproduction, but are distinguished by 



