BOUILLIB BORDELAISE. 247 



a bouillie made with 0-5 per cent of blue vitriol. The third spraying, if 

 necessary, should take place when the leaves have reached their 

 normal size. The result of these operations is not always complete 

 the first year, but the second or the third year the " cloque " will dis- 

 appear if care has been taken of the trees in this way. The " cloque "" 

 will not again appear if one or two preventive sprayings are given 

 every year. The beneficial action of bouillie bordelaise is surprising. 

 It is generally allowed that cupric sprayings can exert no destructive 

 action on fungi, the mycelium of which grows in the interior of the 

 tissues. The preventive use of bouillies in different diseases should 

 have no other object than to preserve the tissues, by preventing the 

 spores which are deposited thereon from producing the disease. It is 

 otherwise in regard to the leaf curl, where the bouillie is used as a 

 curative agent. We know so little as to the method of propagation of 

 the "cloque" (the artificial infection of peach-trees by spores has 

 never succeeded) that we cannot exactly define what is the role played 

 in its suppression by spraying with bouillie bordelaise. We believe,, 

 however, that, in this case the copper compounds deposited on the 

 peach-trees destroy the mycelium of the leaf curl. The peach be- 

 haves in a special way towards cupric compounds. It can dissolve- 

 insoluble cupric deposits on its organs in quantities poisonous to the 

 fungi and itself. It follows that the effect of the bouillie bordelaise on 

 the health of the plant is identical with that produced by spraying 

 with pure blue vitriol. In most cases the use of cupric bouillie, 

 even that of weak bouillie bordelaise, produces the partial or total fall 

 of the leaf reached by the preparation. Those which do not fall are 

 riddled with holes, or seriously attacked. Are we to admit that the 

 mycelium, which almost crawls on the leaf, since it is lodged between 

 the epidermis and the cuticle, and is very little protected by the tissues, 

 undergoes the first poisonous action of the salts of copper absorbed by 

 the leaves? Or must it be admitted that the action of the bouillie 

 bordelaise results solely from the fact that the mycelium localized in 

 the leaves is necessarily suppressed at the same time as the disease by 

 the fall of the leaves? In our opinion beneficial action of bouillie 

 bordelaise results fi'om the two following facts : (1) destruction of the 

 mycelium of the Exoascus lodged in the buds in the spring ; (2) its 

 suppression, by the fall of the infected leaves in which the disease is 

 localized. The fall of the leaves, incidental to the treatment, has r.o 

 deadly action on the evolution of the tree, and there is nothing at 

 which to be alarmed. The copper absorbed by the plant stimulates 

 it, and causes a more rapid and more intense growth, so that the tree 

 in summer and in autumn would be more vigorous than untreated 

 trees. We therefore possess in bouillie bordelaise a curative remedy 

 for the leaf curl of the peach, a remedy which may be of great 

 service to gardeners. We insist, therefore, on this point, that the 

 treatment to be complete should extend several years, and should 

 enter into the common customs of the orchard. Not only the crypto- 

 gamic diseases of the peach will be suppressed, but the quite excep- 

 tional vigour of the trees treated will enable better crops to be secured 

 than on untreated trees. 



