282 TIMBER AND SOME OF ITS DISEASES. [CHAP. 



hour and day after day for several weeks, each hypl 

 producing two or more conidia within a few hours ol 

 its emergence ; hence hundreds of thousands of conidi; 

 may be formed in the course of a few days, and ii 

 we reflect how light the conidia are, and how theii 

 zoospores can flit about to considerable distances, ii 

 is not surprising that many of them are shed on 



FlG. 45. An oogonium and antheridium of Phytophthoraomnivora. The oogonii 

 is the larger rounded body, borne on a branch of the mycelium : it contains ; 

 oosphere, in process of being fertilized by the protoplasm of the antheridium (t 

 smaller body applied to the side of the oogonium). The antheridium has pierc 

 the wall of the oogonium, by means of a fertilizing tube, through which the content 

 pass into the oosphere, converting the latter into an oospore. (Very hi 

 magnified ; after De Bary. ) 



the surrounding seedlings, to repeat the story. If 

 further bear in mind that not only every puff of win< 

 but every drop of rain, every beetle, or fly, or mou: 

 &c., which shakes the diseased seedling may eithei 

 shake conidia on to the next nearest seedlings or eve 

 carry them further, it is clearly intelligible how tl 

 infection is brought about, and spreads through tl 



