is completely sterile without such aid in another district.
Finally, if we consider how precious a substance pollen is, and what care has been bestowed on its elaboration and on the accessory parts in the Orchideæ,—considering how large an amount is necessary for the impregnation of the almost innumerable seeds produced by these plants,—considering that the anther stands close behind or above the stigma, self-fertilisation would have been an incomparably safer and easier process than the transportal of pollen from flower to flower. Unless we bear in mind the good effects which have been proved to follow in most cases from cross-fertilisation, it is an astonishing fact that the flowers of the Orchideæ should not have been regularly self-fertilised. It apparently demonstrates that there must be something injurious in this latter process, of which fact I have elsewhere given direct proof. It is hardly an exaggeration to say that Nature tells us, in the most emphatic manner, that she abhors perpetual self-fertilisation.
