136 MASSACHUSETTS HORTICULTURAL SOCIETY. 



of introducing chemicals directly into the tissues, but so far without 

 any practical results. Interesting efTects from the plant physiolo- 

 gist's standpoint have been recorded, but no one has ever satis- 

 factorily treated any specific diseases by these methods. 



There has been some work published, notably that of Massee 

 working in England, and Beauverie and Laurent in France, indi- 

 cating that immunity to specific . diseases may be produced by 

 watering the soil in which plants are growing with solutions of 

 chemical substances having fungicidal properties. Massee suc- 

 ceeded in rendering tomato and cucumber plants immune to certain 

 greenhouse diseases by watering them regularly with a solution 

 containing one part of copper sulphate to 7000 parts of water, 

 later he increased this to the proportion of 1 : 6000. 



Whether the study of the development by artificial means of 

 disease resistant individuals, as indicated, will be productive of 

 any practical results has yet to be demonstrated. This work is yet 

 in the experimental stage. The work that has already been re- 

 corded needs verification and there is much more to be done. 

 There is excellent opportunity for investigation in this field by the 

 plant physiologist and plant pathologist. 



I hope that I have succeeded in showing my audience some of 

 the possibilities of this phase of plant breeding work and that I 

 have not given a false impression as to the ultimate utility of disease 

 resistant varieties. I wish to lay particular stress on the objections 

 which I have mentioned. At this stage of the work we cannot say 

 whether the difficulties will be surmounted or whether they will in 

 time make the continuation of the study impracticable. 



In resistance we have not a cure-all. It is, however, a prominent 

 adjunct to the increasing number of methods of treating plant 

 diseases. 



Some phases of the work of developing disease resisting varieties 

 are very simple and I hope that I have shown that any intelligent 

 grower may add to the sum of our knowledge of this subject by 

 careful observation of varieties or by selecting seed from individuals 

 which have survived an epidemic. 



Discussion. 

 William H. Spooner remarked that the fire blight of pears in 



