Just how diseases are caught by one plant or section of a garden from another, is not fully known, but we know that insects often carry infection from one to another, as in fruit trees to which bees go for honey. The bee, coming from an infected tree to a perfectly healthy tree, may bring with it the germs of the disease or the eggs of the pest. Many scientific men now hold that plant diseases are transmitted by germs, which are carried not by insects only but also by the wind and the water in the soil. The wrong use of fertilizers or barnyard manure may often induce disease, simply because the unbalanced food supply causes irregularity in growth, which weakens the plant’s resisting power. What is called a “balanced ration,” is of the utmost importance to plants. It is not enough that the soil contain an abundance of some of the elements of plant food, but that it contain all of them in nice proportion, so that the plant can draw all it needs, and not be overfed in some ways and underfed in others. That is why we add humus, why we fertilize, why we cultivate, and why we take note of our plants while growing. Only in this way can we supply their wants. Weeds spread diseases and we should be ashamed of them. Not only are they usually favorable to the growth of insects, scales and blights, but some kinds of weeds actually breed these parasites. Moreover, they rob the soil of nourishment during the dry, hot spells, thus bringing about various kinds of rots and mildews. And now it is supposed that they give out a kind of poison, or excrement, which renders the soil unfit for crops. All this shows the necessity of clean cultivation if we would help our crops to resist both insects and diseases. CHAPTER XI. RE-SOILING. There is a good deal of talk these days about re-soiling, but the word is misleading. We cannot re-soil this earth or any part of it. The soil is there for keeps. It was here before us, and will remain after we are gone. All we can do is to put back into the soil some of the vegetable matter of which we have robbed it; and this is really what we have in mind when we speak of re-soiling. People have the habit of coining almost meaningless words, and then wondering why everybody does not know at once what they meant to say. What we are after is, to put humus, which is really decayed vegetable matter, back into the soil. Then that natural fertility, of which we have been talking, will have a chance to get to work. [Illustration: WINTER RESIDENTS IN A SUMMER CAMP.]