little good, is likewise a strong corroboration of our conclusion; for the sexual elements in the flowers on the same plant can rarely have been differentiated, though this is possible, as flower-buds are in one sense distinct individuals, sometimes varying and differing from one another in structure or constitution.  Thus the proposition that the benefit from cross-fertilisation depends on the plants which are crossed having been subjected during previous generations to somewhat different conditions, or to their having varied from some unknown cause as if they had been thus subjected, is securely fortified on all sides.

Before proceeding any further, the view which has been maintained by several physiologists must be noticed, namely, that all the evils from breeding animals too closely, and no doubt, as they would say, from the self-fertilisation of plants, is the result of the increase of some morbid tendency or weakness of constitution common to the closely related parents, or to the two sexes of hermaphrodite plants.  Undoubtedly injury has often thus resulted; but it is a vain attempt to extend this view to the numerous cases given in my Tables.  It should be remembered that the same mother-plant was both self-fertilised and crossed, so that if she had been unhealthy she would have transmitted half her morbid tendencies to her crossed offspring.  But plants appearing perfectly healthy, some of them growing wild, or the immediate offspring of wild plants, or vigorous common garden-plants, were selected for experiment.  Considering the number of species which were tried, it is nothing less than absurd to suppose that in all these cases the mother-plants, though not appearing in any way diseased, were weak or unhealthy in so peculiar a manner that their self-fertilised seedlings, many hundreds in number, were rendered inferior in height, weight, constitutional vigour and fertility to their crossed offspring.  Moreover, this belief cannot be extended to the strongly marked advantages which invariably follow, as far as my experience serves, from intercrossing the individuals of the same variety or of distinct varieties, if these have been subjected during some generations to different conditions.

It is obvious that the exposure of two sets of plants during several generations to different conditions can lead to no beneficial results, as far as crossing is concerned, unless their sexual elements are thus affected.  That every organism is acted on to a certain extent by a change in its environment, will not, I presume, be disputed.  It is hardly necessary to advance evidence on this head; we can perceive the difference between individual plants of the same species which have grown in somewhat more shady or sunny, dry or damp places.  Plants which have been propagated for some generations under different climates or at different seasons of the year transmit different constitutions to their seedlings.  Under such circumstances,