As an example we may take one of the varieties of wheat originated by the Minnesota Experiment Station. Hays described it as follows. It was originated from a single plant. From among 400 plants of "Blue stem" several of the best were chosen, each growing separately, a foot apart in every direction. Each of the selected plants yielded 500 or more grains of wheat, weighing 10 or more grams. The seeds from these selected plants were raised for a few years until sufficient was obtained to sow a plot. Then for several years the new strains were grown in a field beside the parent-variety. One of them was so much superior that all others were discarded. It was the one named "Minnesota No. 169." For a large area of Minnesota this wheat seems capable of yielding at least 1 or 2 bushels more grain per acre than its parent variety, which is the best kind commonly and almost universally found on the farms in southern and central Minnesota. It would be quite superfluous for our present purpose to give more instances. The fact of [118] the compound nature of so-called species of cultivated plants seems to be beyond all doubt, and its practical importance is quite obvious. Acclimatization is another process, which is largely dependent on the choice of adequate varieties. This is shown on a large scale by the slow and gradual dispersion of the varieties of corn in this country. The largest types are limited to temperate and subtropical regions, while the varieties capable of cultivation in more northern latitudes are smaller in size and stature and require a smaller number of days to reach their full development from seed to seed. Northern varieties are small and short lived, but the "Forty-day-corn" or "Quarantino maize" is recorded to have existed in tropical America at the time of Columbus. In preference, or rather to the entire exclusion of taller varieties, it has thriven on the northern boundaries of the corn-growing states of Europe since the very beginning of its cultivation. According to Naudin, the same rule prevails with melons, cucumbers and gherkins, and other instances could easily be given. Referring now to the inferences that may be drawn from the experience of the breeders in order to elucidate the natural processes, we will return to the whitlow-grasses and pansies.