1911] The Ottawa Naturalist. 135 



and shut off from the food supply. Formations like the enlarged 

 portions of plants, which occur in black knot, plum pocket, 

 club root, etc., are also very common. 



It now becomes necessary to briefly consider the question 

 of the predisposition of plants towards disease. The word 

 predisposition may not be fortunately chosen to describe the 

 peculiar observations that may be made in the direction of 

 resistance or susceptibility towards disease. In medicine as 

 well as in plant pathologv we often meet with typical cases of 

 immunity in animals or plants. For some reason or other some 

 individuals escape a disease altogether, or remain singularlv 

 resistant in recovering unhurt from an attack. Hence, modern 

 investigators claim that the successful selecting of resistant 

 varieties would sooner or later decide the question of treatment 

 for disease. This expectation is undoubtedly quite reasonable, 

 but at present we have only just begun to open our eyes and the 

 results obtained so far have more of a scientific than a practical 

 value. Disease resistance has been established to a certain 

 degree in grain considering the rust problem, but unfortunately 

 the varieties fairly rust-proof showed other undesirable charac- 

 ters, or they were disease-proof onlv in a small locality. We 

 must also bear in mind that the adaptation of disease-causing 

 organisms to new conditions will play a very important role, 

 and at present while there is every hope of improving our know- 

 ledge in this respect, our results are not established long enough 

 to speak the last word in the breeding of disease-resistant 

 varieties. It would, however, be quite erroneous to construe 

 my remarks in a manner in which thev were not intended. 

 While pointing out the difficulties, yet there is every hope of 

 making important discoveries along these lines. 



Next, let us consider the resistance to disease. In medicine 

 we are informed that living according to common, normal 

 sense,- avoiding foods or practices which lead to the weakening 

 of the organism, we will not only reach but maintain a con- 

 dition which we describe simplv as health. Health, to my mind 

 is nothing else but the keeping of body and mind sound by per- 

 forming the normal functions of our organs. Thus, by following 

 closely our needs and bv living correctlv we can bring our bodies 

 into a state of great resistance and even immunity, though we 

 may be living amidst a serious epidemic at the moment. Infec- 

 tious germs, though surrounding us constantly, will have no 

 chance of exercising their serious effect upon us if we are in a 

 perfectly sound state of body. It is quite impossible to avoid 

 contact with disease germs and this being the case, prevention 

 of disease is largely dependent upon success in bringing our 

 organism into a strong condition of resistance. This, of course. 



