xvi.] WHITE-RUST DISEASE OF CABBAGES, ETC. 91 



and termed, in reference to their nature, antheridia, or 

 organs answering to the anthers of flowering plants. In 

 the course of growth the antheridium comes in contact 

 with the oogonium as at B, and projects a fine "beak 

 through its wall, till it pierces the oosphere within as at 

 C. This is the act of fertilisation answering to the dis- 

 charge of pollen on to the stigma in flowering plants. 

 In the same way as an ovule becomes a seed after 



FIG. 33. WHITE RUST OF CABBAGES. 



Oogonium with Antheridium and Resting-spores, or Oospores of Cystopits 

 candidus, Lev. Enlarged 400 diameters. 



fertilisation in flowering plants, the oosphere becomes an 

 oospore or egglike spore, after the contact of the antheridium 

 with the oosphere. The now fertile oospore within the 

 oogonium grows and matures itself whilst still within the 

 supporting leaf or stem for many months, generally for 

 the greater part of a year, and it does not become perfectly 

 ripe till the host plant has decayed. Although the 



