428 



FUNGOUS DISEASES OF PLANTS 



frequently appear spindling from the beginning. Nevertheless, the 

 affected shoots or canes may not be killed, and the disease may 

 reappear upon such affected plants the following year from the 

 growth of the mycelium into young shoots. In the end, practically 

 all affected plants are killed, and their vitality is from the outset 

 so diminished that productiveness is impossible. 



Fig. 208. Blackberry Rust, C^eo-ma Stage 

 To the left, normal shoots ; to the right, diseased 



The fungus. The mycelium of this fungus has been carefully 

 studied in the growing canes. It is intercellular, and grows rap- 

 idly in the direction of formative tissues, or where new cells are 

 being produced, extending but slightly into tissues or organs which 

 have matured. The mycelium is richly provided with haustoria. 

 The tip of the haustorium enlarges as a knob-like organ, and this 

 is commonly more or less in contact with the cell nucleus. The 

 mycelium in the root penetrates the parenchymatic cortical cells, 



