1915] 



SMITH BACTERIAL DISEASES OP PLANTS 



401 



Great care should be taken to keep the manure heap free 

 from infection. Diseased rubbish should be burned or buried 

 deeply. It must not be thrown into a water supply or fed 

 stock or dumped into the barnyard. 



It has been found that some varieties of plants are less sub 



iect to disease than others 



um, maize, potato 



tomato, susrar-cane, banana, cabbajre. etc.). and there 



individual 



These phenomena 



lead us to hope that by selection, or hybridization, valuable re- 

 sistant strains may be originated. Meanwhile the resistant 

 sorts when they are of any value commercially should be sub- 

 tuted for sensitive sorts in localities much subject to the 

 lease. Unfortunately some of the resistant sorts have other 



di 



desirable 



qualities. A vast amount of experimental work 

 must be done in this field before we shall have substantial re- 

 sults, and at least a generation or two will be required to learn 

 even the boundaries of the field. But the problem offered is 

 so enticing and has such immediately practical bearings that 

 in the near future we may suppose many pathologists will de- 

 vote themselves to it, and that long before the whole field is 

 worked over, many useful results will be forthcoming. The 

 labor involved is enormous and exacting to discouragement at 

 times, the results come so slowly, so much must be done to be 

 certain of so little, all because the organisms dealt with are 

 very small — how small, we seldom realize! 



Many a time in the past when downcast I have repeated to 

 myself Seneca's rolling words, Palma non sine pulvere per 

 viam rectam, and have had more or less encouragement out 

 of them. They are a good motto for any man, since nothing 

 is more certain than this, that without plenty of well-directed 

 hard work there can be no worthy success in any field of human 

 endeavor. 



