186 



Studies in Bacteriosls 



brown discoloration of the root cortex (Fig. 1). The frequent occurrence 

 of disease in the seed-bed suggests that the seed from infected fruit may 

 also be infected or carry the causal organism externally though so far 

 no actual proof of this has been obtained. Observations in nurseries and 

 practical experiments have shown that the disease may sometimes 

 spread downwards; successful "prick" inoculations have been made on 



Fig. 1. SlKJVving hrown stripe on tlie rout, of a tomato plant alToct(>d with ".Stripe 



Disease." 



the upper parts of plants and indicate that insects may produce infection 

 of these parts. It is also fairly certain that the pruning knife is a potent 

 factor in sj)reading the disease; in one house it was observed that disease 

 had spread from one end on both sides of the house while in another it 

 had spread a certain distance down one side only, in the former case it 

 was shown that the pruning had been across the house from left to right, 

 while in the latter the pruning had been down one side and up tlu^ other. 



