CYSTOPUS. 125 



Besides conidia, spherical oospores may also be present ; these 

 are generally produced on the stems of the host-plant, but also 

 on flower-stalks and ovary-walls. 



The spherical conidia arise in simple chains on short coni- 

 diophores, and are loosely connected by tiny intermediate cells. 

 The conidial cushions rupture the epidermis and the ripe conidia 

 fall off to produce biciliate swarming cells (Fig. 34). These 

 give rise to germ-tubes which enter the stomata of seedlings and 



Fig. 36. — Flower of Radish hypertrophied by Cyslopus candidus. The white 

 swollen conidial cushions occupy the enlarged petals, sepals and ovaries. (Dr. 

 Bruns' phot.) 



develop to intercellular mycelia, fine short lateral twigs of 

 which pierce the wall of the host-cells and become little 

 spherical haustoria. 



The oogonia arise as thick-walled spherical swellings on the 

 mycelium. The antheridium, after applying itself to the oogonium, 

 widens and projects a fine fertilization-tube through the wall to 

 the egg-cell. After fertilization is effected, the egg-cell is enclosed 

 in a firm uneven membrane, and hibernates inside the oogonium. 

 In spring the plasma of the oospore forms numerous biciliate 



