This section is from the book "The Gardener's Monthly And Horticulturist V25", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
In the Monthly for November, 1882, Mr. Carman writes: "During two seasons past, I have spent much time in crossing wheats. I have been very careful to remove the anthers from each flower while yet they were immature. Whenever they (the anthers) showed a tint of yellow, an indication of approaching maturity, I have destroyed the anthers. Nevertheless, seventy-five per cent. of the heads from plants raised from the crossed seed could not be distinguished from those of the mother plant."
The attempts at crossing as recorded above do not seem to have been successful, and if statements long since given to the public are true they could not have been otherwise. The cause of failure is owing to the fact that wheat, in common with other members of the grass family, is cleistogamous, in all of which cases fertilization takes place while yet the flowers are within the folds of the sheaths. This characteristic can be seen in Vilfa, Leersia and Sporobolus, as well as in wheat; and the remarkable fact also that when the terminal flowers of spike or panicle escape confinement they are less productive of seeds than those which never reach the light.
As having a direct bearing upon this subject, we may be permitted to quote a sentence or two from an article on the cross-breeding of plants by the late D. Beaton, written at the request of C. Darwin. Mr. Beaton says :
"No kind of wheat has ever been naturally crossed, and never can be. When the Royal Agricultural Society talk about the wheat being in blossom, they are' just one month behind nature. But what they and the bulk of the country people take for the flowering of the wheat is one of the most beautiful contrivances in nature as means to an end. A departure from the law of nature, as it were, to preserve food for man. The wheat is in full flower, and the seed is fertilized while the ear is yet in the folds of the sheath, before the wheat is in ear. At that period the anthers might be said to be sessile, or to have hardly any length of stamens under them; but as soon as the pollen is shed, the husk of the anther might rot in such close confinement, and endanger the safety of the staff of life, now having just received vitality. To prevent famine for lack of wheat, however, nature alters her common process in this matter. As soon as the anther is emptied of the pollen the filaments begin to grow, and to push up the husk of the anther away from the embryo seed,.and by the time the ear is seen the husk is well-nigh out of the scales which enclose the seed, but stops not then nor till the husk is dangling from a white thread, far off from the entrance to the seed-case; and when all dangers are thus provided against, the farmer congratulates himself if the weather is propitious, for his wheat is in blossom !"
Thus it will appear that Mr. Beaton recognizes no middle ground upon which to meet those who believe that cleistogamous flowers can be cross-fertilized, and from the evidence adduced he does not seem to be much mistaken. I cannot speak authoritatively in regard to wheat, but having bestowed some attention upon several of the grasses which belong to this class, more especially the different species of Vilfa, it is safe to say, there is not one chance in ten thousand that they ever cross. Even this slim chance may meet the requirements of those who believe that crossing is a necessity in nature, although taking place only at very long intervals. But there is an uncertainty about this which must be removed, before we can see clearly how much or how little species depend upon cross-fertilization for their continuance in pristine vigor.