CRACKED FRUIT--MILDEW.--Certain fruits become partially covered with what appears to be a fungous growth, which occupies the skin in such a manner as to prevent the development of the succulent tissues beneath it. This may result in a deformity consequent upon the irregular growth, and the fruit is called scabby, or it may strike deeper into the tissues, which become dry and corky and crack open, being thus utterly worthless. Some varieties, which formerly produced the most beautiful fruits, have been so severely affected by this malady as to yield absolutely nothing in certain localities, and are only rendered profitable by top grafting with other sorts that are not affected with the cracking. That this is not caused by the wearing out of the variety, as has been suggested, it may be added that the same fruit ripens perfectly and is quite fair in other regions of the country. The trouble, however, is extending, and it is hardly safe to plant largely of those varieties that have proved subject to the malady. No explanation has been satisfactory as to the cause, nor has any treatment been successful. Dr. Kirtland addressed the Ohio Pomological Society upon this subject, and an abstract of his remarks is here given:-- "The disease known as the blight or the fire-blight, is at this day proving the most serious obstacle to the successful cultivation of the pear, in many sections of the country. Early in the present century it prevailed extensively in New England, coincidently with the spotted fever, and other disorders of a low grade of action, which at that period swept epidemically over that region of the country. It was a popular opinion that all these diseases, both of the human family and vegetable kingdom, arose from one cause;--an opinion not, however, tolerated by medical men and men of science in that day. "Various theories have been advanced to account for the origin of this blight. Insects, frozen sap, electricity, excessive evaporation, and exhaustion of the soil, have, at different times, been assigned as the cause. Investigation of each fails to meet and explain the phenomena attendant on the rise, progress, and results of that disease. It is time they all should be abandoned, and that researches for a cause be extended in some other direction. "As a starting point in this undertaking, I will suggest another hypothesis, which may perhaps explain the pathology of the blight, and call into use an effectual remedy or preventive. _Pathology_, Dr. Webster defines to be 'the doctrine of the causes and nature of diseases.' "1. The Pear-tree blight is produced by the poisonous impression of the seeds (_sporules_) of a microscopic fungus. "2. Several combinations of iron, especially the sulphate (_copperas_), will, to some extent, counteract that impression.