Chapter I: DESCRIPTION.—Although the signs of it, as will appear in the

sequel, may be detected long before the leaves put out in the spring, yet its full effects do not begin to appear until May, or if the spring be backward, until June. On the wood of the last year will be found a point where the bark is either dead and dry, or else at the same point the bark will be puffed, softened, or sappy with thickened sap—these two appearances indicating only different degrees of the same blight. Wherever the bark is dead and dry, the limb will flourish above it, make new wood, ripen its fruit, but perish the ensuing winter. In the other case, as soon as the circulation of the sap becomes active, the point described shows signs of disease, the leaf turns to a darker brown than is natural to its ordinary decay, being nearly black, and the wood perishes.

The disease, at first, blights the terminal portions of the branch; but the affection spreads gradually downward, and sometimes affects the whole trunk. The time from the first appearance of the blight to that in which any affected part dies, is various; sometimes two or three weeks—sometimes a day only; and sometimes, but rarely, even a few hours consummate the disease.

On dissecting the branch, the wood is of a dirty, brownish, yellow color; the sap thick and unctuous, of a sour disagreeable odor, like that of a fermented watermelon, on the tops of potato vines after they have been frosted. In still, moist days, where the blight is extensive in an orchard, this odor fills the air, and is disagreeably perceptible at some distance from the trees.

Sometimes the bark bursts, the sap exudes, and runs down, turning black; and its acridity will destroy vegetation on which it may drop, and shoots, at a distance from the trunk, upon which the rain washes this ichor, will soon perish. When we come to treat of the _cause_ of this disease, it will be important to remember this malignancy of the fluids.

We are carefully to distinguish these appearances, peculiar to what I suppose ought to be called _winter-blight_, from another and a _summer-blight_. In this last, the leaf is affected at first in spots; gradually the whole leaf turns russet color and drops. Along the wood may be seen the hardened trail as of a slimy insect, of an ash color. The _wood_ suffers very little by this summer-blight, and sometimes none. The winter-blight is found on almost all kinds of trees. This summer it has affected the apple, the pear, the peach, the quince, the English hawthorn, privet, black birch, Spanish chestnut, elder, and calycanthus. I enumerate the most of these kinds on the authority of J. H. James, of Urbana, Ohio, and C. W. Elliott, of Cincinnati, having observed it myself only on fruit-trees.