MEANS OF PREVENTION AND CONTROL 



1205 



fornia, on the University Farm, were inoculated in 1916, and in all there 

 was an abundant formation of galls. The same results were obtained with 

 P. Armeniaca, P. Armeniaca var. Mikado, P. Mume and P. mandschurica. 

 The major part of the varieties and kinds at present preferred in Cali- 

 fornia as basal material for orchards are therefore, in principle, highly 

 liable to contract crown gall ; on the other hand, there are types, little known 

 as yet, belonging to different groups and especially to the species P. domestica 

 which, if duly controlled and selected, ma^' furnish an excellent renewal 

 stock. 



937 - Prophylaxis in Vegetable Pathology. — Comes Orazio, in Rcale htUnlo d'lnccyra-- 

 i^iamcntu di Napoli, 173 pp. Naples, i()i6. 



The writer points out that though it is still absolutely necessary to 

 resort to therapeutic means whenever the plant is ailing or attacked by 

 parasites, it would be desirable, on the other hand, to take into account what 

 has long been practised in animal pathology. In animals, the extension of 

 the action of hygiene limits the sphere of therapeutics in a greater degree 

 day by day, and in the same way, by more rational attention and more appro- 

 priate measures, the cultivated plant must be made stronger, and more cap- 

 able of resisting the attacks of its enemies ; in other words, greater attention 

 must be devoted to the hj'giene of the plant. 



Yet it must not be forgotten that sensitiveness to bad weather and re- 

 ceptivity to parasites vary in plants with age, methods of cultivation, and 

 the environment in which they are grown. Furthermore, ordinary practice 

 shows that the resistance to adverse agencies varies in cultivated plants with 

 the different races, and, in the same race, with the individual. It follows 

 that on the whole, the resistance is rather individual than specific. In view 

 also of the remarkable influence of the environment and methods of culti- 

 vation on the plant, it must be expected that this influence will be clearh^ 

 reflected in the capacity of resistance of the plant, even if the latter be modi- 

 fied so as to render receptive plants considered as immune, and also to 

 cause fungi considered as inoffensive or at least as semi-parasitic to become 

 injurious. 



On the other hand, from the biological point of view, it cannot be main- 

 tained that there are absolutely imnume races ; nevertheless, such steps may' 

 be taken as to ensure that their resistance to adverse factors should not be 

 reduced so as to jeopardise their productivity. This object might be ob- 

 tained by hygiene and prophylaxis. The latter alone could little by little 

 lead to the abolition of the empirical methods which still predominate ; 

 by guiding vegetable pathology once for all along a rational path, it will 

 result in rendering intensive agriculture more economical, in spite of the 

 evergrowing delicacy of its products. 



Such is the theory maintained by tlie writer, and the object of his 

 article. He reviews an extensive series of observations and researches 

 collected from the literature on the subject. 



His work is divided into two parts ; in the first he deals with plant 

 susceptibility to disease, and in the second with resistance. 



As regards the susceptibility, the influence of the climate, soil, cultiva- 



MEANS 

 OF PREVENTION 

 AND CONTROL 



