When conditions are undisturbed by man there is found to be a fierce struggle for existence. The hardiest or those best suited to the conditions preponderate, and this without any reference to the wants of mankind. The farmer steps in and selects those plants which give promise of being most useful or most beautiful and then decreases or eliminates the struggle for these selected plants, by destroying the plants which are least desirable, by fertilizing and tilling the soil, by conserving moisture, and by improving the physical conditions of the land, thereby making it more comfortable for the plants which he has chosen. The selected or "improved" plant, by reason of being more comfortable and better nourished, tends to vary in one or more directions from the wild and unimproved types. Whenever these variations tend towards greater productiveness, better quality or enhanced beauty, selection is again made of such specimens as give promise of supplying the wants and gratifying the desires of civilized man. The bettered conditions of the plant, by reason of man's effort, do not usually result in producing like variation along all lines. One part of the plant as the flower, the fruit, or the stem, varies more than the other parts. All this tends to break up a single type or stock into many varieties. There are hundreds of varieties of potatoes all traceable to a single wild species. The kind and quantity of nourishment supplied plays the most important part of any single factor in producing variation. The general character of the cultivated potato plant as to leaf, stem, root, and habit of growth, is virtually the same as the wild plant, variation having been directed and accentuated along the line of increasing the size and quality of the underground tubers. This habit of producing enormously enlarged underground stems has been operating so long that the plant has inherited the power of transmitting this acquired quality to the succeeding plants. The most improved varieties seldom produce seed balls, because growth has been directed so largely toward enlarging and multiplying the tubers. By selecting tubers with shallow buds or eyes and avoiding those with deep, sunken eyes, varieties have been produced with few eyes or buds, and these set not in deep indentations but nearly even with the surface of the potato. * * * * *