284 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



oecomes collected into a ball (the egg-cell or oospJtei 

 and then a smaller branch with a distinct origin appli< 

 itself to the outside of this rounded swelling ai 

 pierces its wall by means of a narrow tube : protoplasi 

 from the smaller branch (antheridium) is then poui 

 through the tube into the "egg-cell," which thi 

 becomes a fertilized " egg-spore " or oospore. Tl 

 oospore then acquires a very hard coating, and posses* 

 the remarkable peculiarity that it may be kept in 

 dormant state for months and even a year or m< 

 before it need germinate : for this reason it is oft< 

 called a resting spore. It has been found that al 

 700,000 oospores may be formed in one cotyledon, an< 

 a handful of the infected soil has sufficed to kill 

 seedlings. 



Now, when we know this, and reflect that thousam 

 of these oospores are formed in the rotting seedling 

 and are washed into the soil of the seed-bed by tl 

 rain, it is intelligible why this seed-bed is infectec 

 If seeds are sown there the next spring, the younj 

 seedlings are attacked as soon as they come up. 

 These oospores are, in fact, produced in order that the 

 fungus shall not die out as soon as it has exhausted 

 the current year's supply of seedlings ; whereas the 

 conidia, which soon lose their power of germinating, 

 are the means by which the parasite rapidly extends 



