14. Many weeds interfere with a rotation of crops.
15. All weeds damage the appearance of a farm and render it less valuable. (Quack-grass, Canada thistle, plantains.)
SOME SMALL BENEFITS.
1. They are of some use in the world to induce more frequent and more thorough cultivation, which benefits crops.
2. The new arrival of a weed of first rank stimulates watchfulness. (Russian thistle.)
3. In occupying the soil after a crop has been removed they prevent the loss of fertility by shading the ground.
4. Weeds plowed under add some humus and fertility to the soil, though in a very much less degree than clover or cow peas.
5. Some of them furnish food for birds in winter.