Pear Blight.

THE TWO THEORIES WITH REGARD TO ITS CAUSE, AND THEIR PRACTICAL VALUE.

It is assumed that this pest has cost agriculturists many millions of dollars during the past decade; not only in the loss of trees, but the time—as it seldom appears until after the first crop—consequently the land, manure, labor, enclosure, and taxes are not insignificant items. Climate, soil, and cultivation have utterly failed, so also the nostrums, such as "carbonate of lime" suggested by the best authority, and the experts now admit that parasites (such as cause the rust or smut in our cereals) are the cause of this mischief. The only question is whether they act directly or indirectly: this question determines whether it is remediable. If these parasites accomplish all this mischief by direct contact, as in the case of rust, their ubiquitous character is so demonstrated that we are utterly discouraged; whereas, if we prove that their indirect action is the only one that is to be dreaded, and that indirect action is remediable we are encouraged to cultivate the pear, though we have lost more than five hundred of one variety and almost all of the other varieties before we discovered the real cause of the failure. "Where you lose you may find;" success does not indicate merit, and "fools never learn by experience." As a celebrated surgeon said in his lecture. "A good oculist is made at the expense of a hatful of eyes."

The celebrated Johnson who wrote the Encyclopedia of Agriculture a few years since, is now regarded as an old fogy, because he assumed that the spores of smut travel from the manure and seed of the previous crop in the circulation of the plant to the capsule, and thus convert the grain into a puff-ball, so also the ears of corn, the oats, and rye. This monstrosity on the rye grains is called ergot, or spurred rye, and when it is eaten by chickens or other fowls their feet and legs shrivel or perish with dry gangrene, not because the spores of the fungus which produced the spurred rye circulate in the blood of the chicken, nor that the spawn or mycelium thus traverses the fowl, but the peculiar and specific influence acts upon the whole animal precisely like the poison of the poison oak, producing its specific effect on the most remote parts of the system, and not as mustard confined to the part it touches. The mustard acts directly, but the "poison Ivy" acts indirectly; so also the virus of cow-pox poisons the whole system, but usually appears in but one spot unless the lymphatics of the whole arm are weak, and in that case crops of umbilicated pustules precisely like the original, may recur on all parts of the arm for several months. The specific effect of ergot or the fungus when indirect is manifested by contracting and even strangulating the tubes or capillaries causing them to pucker up (as a persimmon acts directly on the mouth), but in this case permanently though indirectly, so that rye bread sometimes causes dry gangrene in the human subject; the shins and feet shrivel precisely as those parts of the limbs of the pear do, moreover a dark fluid exudes (as the circulation is arrested where a patch occurs) in both cases alike, consequently if the remedy in both cases is based on the same principles, and is demonstrated to be equally effectual, the cause and the disease are similar.

I have seen dry gangrene in the human subject originate apparently from an old "frost bite;" which means merely chronic debility of the capillaries of the foot or shin. Thus the extremities of the pear, or the weakest part, always succumb first, and the most vigorous trees never manifest it until they are weakened by their first crop of fruit. All are familiar with the fact that an old frost bite will swell or succumb to a temperature which will be innocuous to any other part of the body. The microscope may invariably reveal fungi in the patch of pear blight precisely as the housewife discovers the mold plant in her preserves and canned fruit, and even in the eggs of fowls, the mycelium (or spawn) penetrating the fruit or preserve though it be covered while boiling hot. If so, the reason why all parts of the tree are not attacked at the same time, is not because the fungus is not ubiquitous. We first notice the action of strychnia in the legs, or in paralyzed limbs exclusively, because they are weaker and become subject to its influence more easily; so also the same tree may escape for a long time after the limb which has succumbed is removed. Moreover the grafts, however numerous, may all be blighted, but the standard seedling on which so many varieties were grafted has survived more than fifty winters, and it fruited last year.

David Stewart, M. D. Port Penn, Del.