Dr. G. C. Caldwell, of Cornell, has looked this matter up quite thoroughly. The changes which take place in ripening are somewhat similar to the changes in rotting. In ripening, the abundant starch of the green fruit is changed to cane sugar; later a great part of the cane sugar becomes glucose. These changes may go on while the fruit is still on the tree, or in the storage-room after it has been picked. This change of cane sugar to glucose does not help the fruit in flavor, for glucose is less sweet than cane sugar. The riper fruit gets, short of decay, the sweeter it gets, not because the cane sugar changes to glucose, but because so much of the starch, which is tasteless, becomes sugar and some of the acids of the fruit are decomposed. As fruit goes on to rot, what cane sugar there is goes to glucose, and then this glucose is decomposed. The proteids and the tannin also are decomposed, and new chemical compounds are produced which cause the brown color and the unpleasant taste of the decay which has now set in. Different species of fungi cause this rotting of the fruit, and the three important ones are Penicillium glaucum, Botrytis Vulgaris, and Oilium fructigenum. The last mentioned one exists even on the fruit-trees, and attacks both the ripe and the green fruit, and is even found on the blossoms. It goes in at the stem of the fruit, into the twig and the leaves, and kills both, producing the twig blight and leaf blight, so common. Flies and wasps and other insects carry this fungus from tree to tree.. The more flies and wasps there are about, the more decayed fruit there is. These fungi of decay produce a poison which kills the cells of the leaves and of the twigs and of the fruit.

Now, as to spraying for these fungi with copper and arsenic, even if we spray late, when the fruit is grown, there is little trace of the poisons on the fruit, and they are safe to eat. I have several years since experimented with fungicides sprayed on apples in winter storage in Delaware, and at the time I thought the results were good. The great increase in these fungi over the times of fifty years ago, together with the higher temperature of our cellars where our fruit is often stored, are the great reasons why our fruit does not keep now like it did in the cellars of our grandfathers. General cold storage is coming in to remedy all this and to decrease, I trust, the development of the fungi of decay.