The large kernels of corn and grain, of beans and peas, and even of the lupines were considered by Darwin and others to be unable to cope with natural conditions of life. Many valuable fruits are quite sterile, or produce extremely few seeds. This is notoriously the case with some of the best pears and grapes, with the pine-apples, bananas, bread-fruits, pomegranate and some members of the orange tribe. It is open to discussion as to what may be the immediate cause of this sterility, but it is quite evident, that all such sterile varieties must have originated in a cultivated condition. Otherwise they would surely have been lost. In horticulture and agriculture the fact that new varieties arise from time to time is beyond all doubt, and it is not this question with which we are now concerned. Our arguments were only intended to prove that cultivated species, as a rule, are derived from wild species, which obey the laws discussed in a previous lecture. The botanic units are compound entities, and [91] the real systematic units in elementary species play the same part as in ordinary wild species. The inference that the origin of the cultivated plants is multiple, in most cases, and that more than one, often many separate elementary forms of the same species must originally have been taken into cultivation, throws much light upon many highly important problems of cultivation and selection. This aspect of the question will therefore be the subject of the next lecture. [92] LECTURE IV SELECTION OF ELEMENTARY SPECIES The improvement of cultivated plants must obviously begin with already existing forms. This is true of old cultivated sorts as well as for recent introductions. In either case the starting-point is as important as the improvement, or rather the results depend in a far higher degree on the adequate choice of the initial material than on the methodical and careful treatment of the chosen varieties. This however, has not always been appreciated as it deserves, nor is its importance at present universally recognized. The method of selecting plants for the improvement of the race was discovered by Louis Vilmorin about the middle of the last century. Before his time selection was applied to domestic animals, but Vilmorin was the first to apply this principle to plants. As is well known, he used this method to increase the amount of sugar in beets and thus to raise their value as forage-crops, with such success, that his plants have since been used for the production [93] of sugar. He must have made some choice among the numerous available sorts of beets, or chance must have placed in his hands one of the most appropriate forms. On this point however, no evidence is at hand.