Page:Popular Science Monthly Volume 43.djvu/89

Rh which grow nearly everywhere when circumstances favor them. Their spores seem to be almost omnipresent, but they do not possess the ability to penetrate tough substances, and the natural skin of the apple is usually a barrier they can not pass. Of all these molds the Penicillium glaucum, Lk., or commonly known as the "blue mold," is the one that causes the greatest destruction in the storeroom. A large part of the rapid soft rot is due to the Penicillium.

In a few words let the work of the scab fungus be reviewed. As the name indicates, it causes a scab upon the surface, the



naturally smooth, tough skin is roughened, and minute cracks are produced which in short replace the ordinary skin, impervious to the blue mold, with a disrupted coat that furnishes both a fine lodgment for the spores of the mold and the condition favorable for their germination and the further rapid growth of the mold. It is easy to conceive of the scab upon an apple being so slight and superficial as not to affect its real value, but the one defacement becomes the entrance of a decay germ, that in a few days reduces the whole apple to a noisome mass of rottenness resulting in a million spores or blue mold. To prevent the soft rot of the apple in midwinter in the barrel, the trees need to be sprayed in midsummer in the orchard, to check the development of the scab that would otherwise furnish the place of entrance of the blue mold. Fig. 3 shows an apple that, when harvested, had a number of rough circular patches due to the scab fungus. When the photograph was taken, each one of these spots was the seat of a