1-71 



IMIOTKCTION AGAINST FUNGI. 



the soil. These rhizomorphs readily communicate the disease 

 to roots of iieighhoiiring plants, as in the case of the lioney 



fUHilUS. 



The method of infection is very interesting ; as the tap-root, 

 except at its lower extremity, is protected by cork, the shoots 

 of the mycelium attack the side roots. At the places where 

 these branch off from the main roots, little fleshy swellings 

 are formed, which send out conical processes through the cork 

 into the inner tissues of the tap-root. The fungus grows only 

 in damp warm weather, and if the weather be dry, the infected 

 plant can delay the progress of the fungus, by cutting it oflf by 

 cork-formation from the still healthy tissue^s. By means of 

 the sclerotia, the fungii.s can i)ersi.st thiough dry periods, or 



