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.
As a school-room subject, the potato is not very tractable, unless we study merely the tubers. If the school is in session in summer, the growing plant may be had. Then it will be found to be an interesting and profitable exercise to set the children at the problem of determining the root-system of the potato plant. How do the roots look? Does the plant have a tap-root, or do the roots spread laterally? Are the tubers borne on roots? Or on underground stems? Why do you think so? Does the tuber terminate the branch? What relation, in position, do the tuber-bearing branches bear to other parts of the underground system? Do you think that the tuber-bearing branches aid in collecting food from the soil?
The top of the plant may be studied in the same spirit,—branching, leaves, flowers, berries.
If the growing plant cannot be had, study tubers. Compare as to size, shape, color, character of eyes, whether scabby or smooth. Use them as objects in drawing.
Plant tubers in the school-room, in boxes or flower pots. This Leaflet will suggest some interesting observations.
How important is the potato crop in the State and nation? The pupil can use his mathematics here.