[198-200]

Stolons of Strawberry

Left Hand 20th Fig 4

True Scale for Part of day. Fig. 3.A

[200v]

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Chapter O. 9

therefore thought the foregoing details worth giving. For instance, the sterility of many animals and plants under changed conditions of life, such as confinement, evidently comes under within the same general principle of the sexual system being easily affected)

(As it has already been proved on the one hand, that a cross between plants which have either been self-fertilised or intercrossed during several generations, being & have been kept all the time under closely similar conditions, does not benefit the offspring; and that on the other hand, a cross between plants that have been subjected to different condition benefits the offspring to an extraordinary degree, we may conclude that some degree of differentiation in the sexual system, is necessary for the full fertility of the parent-plants and for the full vigour of their offspring. We may It seems therefore infer probable that with those plants which are capable of self-fertilisation, the male and female elements and the selected parts of plant which are capable of self-fertilisation organs differ to an extent sufficient to excite their mutual interaction; but that when such plants are taken to another country and become in consequence self-sterile, their sexual elements and the selected parts organs are so acted on as to be rendered too uniform for such interaction, like those of a