BOUILLIE BORDELAISE, 233 



not soluble enough in water to prevent the germination of the spores 

 nnost sensitive to copper salts, even after prolonged treatment with 

 them (Aderhold and Eumm). To understand the action of bouillie 

 "bordelaise, it is, however, necessary to admit that there is a partial 

 •solution of oxide in the water deposited on the plant owing to the con- 

 "tact of this oxide with the active organs of the latter. Clark, in ex- 

 amining the poisonous capacity of the most diverse derivatives of copper 

 •on fungi cultivated in a nutritive liquid, beet extract, observed that this 

 liquid dissolved cupric hydrate. Examining afterwards other substances 

 •of vegetable origin, he iound they had the same property. This led 

 him to believe that hydrated oxide of copper insoluble in water is much 

 less so in presence of special organic substances. Swingle had already 

 shown that the secretions of certain fungi dissolve cupric hydrate. 

 ■Clark found afterwards that extracts of Psaliote cavvpestris, as well as 

 infusions of different parasitic fungi, dissolve this oxide of copper in 

 sufficient quantity to prevent the germination of their spores. The 

 nature even of the fungi would thus contribute to dissolve the amount 

 of cupric hydrate required to prevent the development of the spores. 

 The rapidity with which the spores are destroyed depends on the 

 thickness of the exospore. On the other hand, Sorauer believes that 

 the spore is never killed by the presence of cupric hydrate in the 

 drop of water in the midst of which it is developed, but that, on the 

 .other hand, this copper derivative, by weakening it, prevents the ger- 

 mination tube from penetrating into the nurse plant. Hence, spraying 

 with bouillie bordelaise on a plant invaded by a fungus is never cap- 

 able of destroying the mycelium of this fungus developed in the 

 interior of the plant. It cannot even prevent the latter from fructify- 

 ing normally, and spreading around it spores to propagate the disease. 

 "The sole object of spraying with bouillie bordelaise is to prevent the 

 penetration of these spores into healthy uuattacked plants or their 

 -organs. When spraying is done in the right conditions, the bouillie 

 bordelaise covers all the vulnerable surface of the plant with a layer 

 -of cupric hydrate. This layer forms a fixed and adherent reserve of 

 a poison of which an infinitesimal quantity dissolved by the juices of 

 the leaf stops the normal evolution of the spore fallen on a drop of 

 'dew. At the same time the very small quantities which penetrate 

 into the plant, impart to it greater vigour which enables it to become 

 to a certain extent immune to the disease. 



Use of Bouillie Bordelaise. — History. — It was found by a chance 

 •observation, that a mixture of lime and copper might be useful in the 

 struggle against cryptogamic diseases. To prevent marauders from 

 gathering the ripe grapes on vines along the roads it was customary, 

 long before the appearance of mildew, in the different communes of 

 Burgundy to spray the grapes with milk of lime, to which was added 

 a little blue vitriol to blue it. They treated five to six stocks in the 

 •border in this way. Now, as far back as 1882 it was found that these 

 borders were less subject to mildew than the rest of the vineyard, and 

 ■when the disease assumed extensive and intensive proportions, as was 

 the case in 1884, round about St. Julian, this border bespattered by 

 milk of lime, blued by blue vitriol, appeared quite detached from the 



