THE CURRANT TUBERCLE 



437 



with the red rust of the raspberry and blackberry, there is a per- 

 ennial mycelium, living within the tissues of the plant. There is, 

 therefore, no cure. To dig and burn the affected bush at once is 

 the only sure preventive against further spread. Mr. Durand 

 finds* that the mycelium may show no indication of its presence 



Fig. 79. Leaf-spot. 



until long after entering the plant, and that the disease may 

 therefore be transmitted in apparently healthy cuttings. This 

 being true, it follows that cuttings should not be used from a 

 field known to be infected. Since the fungus develops so readily 

 in dead wood, the refuse from pruning should not be left in the field. 



*Loc. cit. 



