Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/281

. IX. lying quite loose. These grains, from their embedded position, could never by any possibility have been left on the stigma of a flower, and were absolutely useless. Those who can persuade themselves that purposeless organs have been specially created, will think little of this fact. Those on the contrary, who believe in the slow modification of organic beings, will feel no surprise that the changes have not always been perfectly effected,—that, during and after the many inherited stages of the abortion of the lower pollen-grains and of the cohesion of the elastic threads, there should still exist a tendency to the production of a few grains where they were originally developed; and that these should consequently be left entangled within the now united threads of the caudicle. They will look at the little clouds formed by the loose pollen-grains within the caudicles of Orchis pyramidalis, as good evidence that an early progenitor of this plant had pollen-masses like those of Epipactis or Goodyera, and that the grains slowly disappeared from the lower parts, leaving the elastic threads naked and ready to cohere into a true caudicle.

As the caudicle plays an important part in the fertilisation of the flower, it might have been developed from one in a nascent condition, such as we see in Epipactis, to any required length merely by the continued preservation of varying increments in its length, each beneficial in relation to other changes in the structure of the flower, and without any abortion of the lower pollen-grains. But we may conclude from the facts just given, that this has not been the sole means,—that the caudicle owes much of its length to such abortion. That in some cases it has subsequently been largely increased in length by natural selection, is highly probable; for in Bonatea speciosa