No satisfactory cause has been assigned at any of the meetings where the subject has been discussed, for the rust and cracking which injures some varieties of the pear and apple, and particularly the Virgalieu or White Doyenne, among the former, and the Early Strawberry among the latter. Nor in the published proceedings of pomological societies, has any definite cause been stated to which this defect may be attributed.

M. J. Berkley, one of the ablest continental writers on these abstruse branches of natural philosophy, presents the following particulars, which, we presume, refers to the malady in question: -

"Species of mould of the family of Helminthosporium, or Cladiosporium, become dreadful pests on the leaves of pears and apples, especially of the former.

" The Cladiosporium dendriticum (of Walroth) arises uniformly beneath the true cutiole,nnder which its mycelium (or spawn) radiates in every direction. It exhausts the strength of the leaves, and often kills the young twigs; while, on the fruit, it forms unsightly black patches, rendering it unsalable, and sometimes inducing, or else accompanied by, extensive cracking. When once it has attacked a tree, it is very apt to return in succeeding years.

" A new progeny raised from the seed of diseased individuals, will exhibit the parental malady".

The same writer recommends as the only probable remedy he knows, the collecting and burning of the infected leaves and shoots, and the application to the buds and remaining portions of a mixture of sulphur, lime and gum tragacanth, the latter to make the mixture permanently adhesive, the former to act on the deposited spores (seeds).

No other remedy is known when the malady has been established. We presume this is the rust and cracking so much complained of as infesting our Virgalieu Pear, by Eastern cultivators. Those who have abandoned the cultivation of the Virgalieu or White Doyenne, working their trees of that variety with others not so subject to the disease, only partially remedy the evil, as the sorts substituted will doubtless become infested if the foregoing statements are correct. The true policy would be to destroy the whole tree, or so to wash it as to destroy all trace of the cryptogamic pest. As the rust and cracking is more prevalent in some localities than others, some predisposing cause must encourage the propagation of this mould; this is either to be sought in the atmospheric peculiarities of the locality, or in the nature of the soil. It is said the more the soil of a district becomes cultivated or worn out, the more the Virgalieu, St. Michael, or White Doyenne, will rust and crack.

Unfortunately for our fruit growers and farmers, attention to practical science is not a characteristic of our country. We have only a few energetic botanists, whose labors are not appreciated as they should be. The New York State Agricultural Society has conferred a great benefit on the farming community by the circulation of Dr. Fitch's essay on insects; what association will call to the aid of the farmer and gardener some able cryptogamic botanist and physiologist ? S.