25 



is bored slowly down into the wood to the desired deptli so that the liquid 

 but no air can penetrate into the canal thus formed by the gimlet. The 

 author who had constructed other apparatus also mentioned Hartig's ex- 

 periments which had the disadvantage of letting air penetrate into the 

 wound. He then began experiments on the healing of chlorosis which were 

 carried out in 1895-6 and in 1901, by garden owners in the Crimea. 



Later Mokrzecki^ published a number of successful experiments 

 on the healing of chlorosis in fruit trees carried out according to the above 

 method, in which he also pointed out that the scale had disappeared from the 

 healed branches. He, as well as Schewyrjov, built great hope on this pro-, 

 cess, not only for the prevention of constitutional disturbances in nutrition 

 but also especially for the expulsion of parasitic organisms. 



■ My personal attitude toward this question is much cooler and I think 

 that the effectiveness of the methods will be very limited. According to my 

 experiments on the introduction of poisonous solutions into the trunk, the 

 effect usually remains local but in the most successful cases radiates grad- 

 ually from the point of introduction to a number of branches and to a con- 

 siderable distance into the trurik. The constitution of the plant, conditioned 

 by root nutrition, was not changed by this. I found in my experiments with 

 oxalic acid that gum was produced on a number of cherry tree branches 

 which later partially died. However, the production of gum did not progress 

 further the following year and the trees, moreover, made a healthy growth. 

 Like this poisonous solution, each nutritive mixture or healing serum remains 

 limited within narrow boundaries and, as in the most favorable case, only 

 temporarily exercises any beneficial influence. The physiological direction 

 of the work of the whole plant will not be changed permanently. 



7. Predisposition. 



We term "predisposition" that condition of certain individuals which 

 renders them more easily and c[uickly susceptible to any cause of disease than 

 are other individuals of the same kind. 



That such cases exist is proved by daily discoveries as to the quantitative 

 growth of cultivated plants. These discoveries have already found expression 

 in the common use of the terms tender and hardy varieties and individuals 

 which have been made less resistant. Observations show that not only differ- 

 ent cultural varieties of the same species but even single individuals of the 

 same variety possess a varying power of resistance to weather extremes, as, 

 for example, cold and heat, or to parasitic attack. In the latter connection, 

 it suffices to mention that practical workers as well as scientific investigators 

 have now set themselves the task of breeding more resistant varieties. 



At present we are only in a position to indicate the direction in which a 

 greater individual inclination to succumb to any parasitic attack rnay be pro- 



1 Mokrzecki, S. A. Ueber die innere Therapie der Pttunzen. Zeitschr. f. 

 zenkrankheiten. 1903. p. 257. 



