230 INSECTICIDES, FUNGICIDES, AND WEED KILLEES. 



than trees which prematurely shed their leaves by degeneration induced 

 by parasites. Numerous comparative trials have shown in an irrefu- 

 table manner, that young fruit trees in the nursery, treated with four to 

 seven sprayings with a 2 per cent bouillie bordelaise, show an increased 

 height, and yield crops largely compensating for the cost of this treat- 

 ment. In nurseries young pears treated three years in succession 

 attained a height of 5 feet to over 7 feet, and had a diameter of 74- 

 inches, whilst untreated pear-trees of the same age, placed in the same 

 conditions, only reached 2-3 feet in height and only 2^-3^ inches in 

 diameter. If the market value of young pear and cherry trees, treated 

 together for three years, be compared with similar untreated trees, 

 there is a gain after deduction of all the cost of treatment of 52 shillings 

 per 1000 trees. With young pear-trees the experiments were not sO' 

 decisive, as their leaves are often sensitive to bouillie bordelaise. The 

 same observations have been made as regards the vine. To obtain a 

 richer growth large doses of copper are not necessary. It is now 

 believed that 0"25 per cent, and even O'l per cent, do the same good 

 as 1 per cent bouillies. Bessler, by one spraying of bouillie bordelaise 

 on haricots when tilling the ground, followed by one spraying of the 

 young plant, obtained a 50 per cent better crop than on untreated 

 plants. It is only the stimulating and preventive treatment which 

 gives this result. 



We must not wait until plants show signs of cryptogamic diseases- 

 before treating them, but prevent such by destroying the germs. 

 Some plants, however, do not stand the deposition of hj^drated oxide 

 of copper on their leaves without injury, because, owing to the ex- 

 ceptional nature of the foliageous tissue, it is absorbed in too great 

 quantity, and then acts like blue vitriol. The plants which behave 

 thus are apple-trees, peach-trees (Sturgis, Miiller, Thiel), and some 

 vai'ieties of rose bushes. On these trees the treatment is followed by 

 the fall of all the leaves reached by the bouillie bordelaise, or at least 

 by burns which cause holes in the leaves. Miiller and other observers 

 found that these burns especially occur when the plant is exposed to 

 the san, and that plants in the shade do not show these injuries. 

 Amongst apple-trees the most sensitive are Canada Cordon, Bellefleur 

 jaune, Eibstone pippin, Danziger Kantapfel. On these species the 

 leaves appear riddled with holes after treatment. Trials, to see if 

 lime contributed to the injurious action of the bouillie bordelaise, have 

 shown the contrary. Whilst a 4 per cent milk of lime has no injurious 

 action on bouillie bordelaise, a 0-5 per cent solution of blue vitriol and 

 a 1 per cent milk of lime burnt the leaves as much, and even more, 

 than a bouillie with 4 per cent of lime and -05 per cent of blue vitriol. 

 The peach-tree — the most sensitive to bouillie bordelaise — behaves to- 

 wards it as towards pure blue vitriol. The treatment is followed in most 

 cases by the fall of the leaf ; but after this treatment the peach, 

 nevertheless, shows the same recrudescence in its vitality as soon as 

 the new leaves come forth, so that in the end this treatment is as 

 salutary as for other trees. The action of cupric hydrate is thus ana- 

 logous to that of green vitriol ; in a general way this salt increases the 

 chlorophyll, and consequently the assimilation ; it thus prolongs the 



