6 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



carbonate, and (b) the aerial or above-ground parts of plants by 

 sulphuring, multiple spra3'ing with weak cupric bouillies, washing of 

 the stock with ferrous sulphate (green vitriol), and by scalding or 

 hot water treatment. The number of plant diseases daily increases, 

 as now we do not solely cultivate native plants, but more and more 

 foreign species imported into the country. The deportation of the 

 latter places them in new conditions against which nature has not 

 armed them ; and in the country of their exile they are defenceless 

 against parasites. But these plants import parasites which find a 

 favourable medium for their evolution in the plants of our country, 

 against which the latter are not armed. Thus it is that very severe 

 diseases have appeared in our crops, and that America has been 

 dowered with parasites, harmless with us, but formidable enemies in 

 that new country. 



Therapeutics. — Therapeutics is that part of medicine which treats 

 of curative agents and studies the manner of using them in the treat- 

 ment of disease. Vegetable therapentics is based on physiological 

 data on the knowledge of the physico-chemical properties of curative 

 agents, on their action (1) on the plants to be treated, (2) on the 

 factors which cause the disease. It will therefore be necessary to 

 indicate in the case of each chemical product used in the treatment 

 of plant diseases (1) The process of manufacture of the chemical 

 product. (2) Its physico-chemical properties, a knowledge of which 

 facilitates the preparation of therapeutic specialities and makes known 

 their mode of action. (3) Its use in human medicine, (4) Its action 

 on the plants treated. (5) Its action on the parasites to be overcome, 

 or on the factors injurious to plants. Curative treatment is surgical 

 when the effective causes are suppressed without the aid of chemical 

 products, and chemical when recourse is had to the aid of chemical 

 products. The use of the one does not exclude the use of the other, 

 and the two utilized simultaneously may produce a better effect. 



Surgical Treatment.— Surgery, or operatory medicine, is the 

 part of medicine which comprises the intervention of the naked hand 

 or the hand armed ^oith mstruments. The intervention of the hand 

 armed with instruments has given rise to vegetable surgery, the inter- 

 vention of the naked hand to the metJwds of destructivn of 'parasites — 

 picking, collecting, trapping, baiting. 



Vegetable Surgery. — Vegetable surgery has many analogies with 

 animal surgery. An organ deeply attacked or capable of being regarded 

 as a seat of infection should be removed in either case. That is so 

 much the more easy in the case of a plant, as the latter is a being 

 whose growth, by budding, is indefinite, and that the organs removed 

 are replaced by equivalent organs in a comparatively short time. 

 The researches of Eeaumur, Ratzeburg, Eobert, Count Jaubert, and 

 Knight have shown how vitality may be restored to a sickly tree. 

 The best known process, called " phloioplasty," consists in removing 

 in a partial or general way the old bark from the trunk and large 

 branches of a diseased tree as far as the liber. The dressing of the 

 wounds, which ought to be kept as clean as those of man, is done 

 thus : If the disease be so deep seated as to necessitate exposing the 



