Part 49. How varieties arise. Finally, a brief consideration of how such "artificial" varieties arise, will help us to understand why it is that long and widespread cultivation should tend to increase the number of these varieties. It will be remembered that when discussing what is meant by a "variety" as distinguished from a "species" (section 9) the statement was made that no two individual plants are exactly alike even though raised from seeds of the same parent. Sometimes the differences are very noticeable, and may affect the plant as a whole, or any part, with reference to size, form, flavor, proportion of chemical constituents, time of appearance or ripening, hardiness, and so on. Since in plants which are raised from seed, the special peculiarities of the parent are found to reappear in its offspring to a greater or less degree, it becomes possible for the farmer to preserve in future crops the peculiarities which please him, by taking his seeds from those individual plants which satisfy him best. Thus if early ripening is the quality desired, the earliest seeds are the ones chosen year after year, until in the course of several, or it may be many generations, furnishing earlier and earlier plants, the offspring finally produced from these selected seeds are found to ripen their product so much sooner than any other sorts that they are recognized as a new variety.

With many plants, such as strawberries, the seedlings are apt to vary so widely from the parent and from each other that the varieties are said to be "not true to seed": and in these cases it is the practice when once a seedling possessed of desirable qualities has been obtained, to propagate it by means of "cuttings" or similar detached portions of the parent plant instead of by seed.

Occasionally important differences appear among the individuals raised from cuttings or the like, and these may similarly form the basis of new varieties.