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He took the fatal double problem of Sprengel as shown at E and F, to express the consummation pictorially and by the simple drawing of a line, as it were, as indicated between G and H, instantly reconciled all the previous perplexities and inconsistencies, thus demonstrating the fundamental plan involved in floral construction to be not merely "insect fertilization," the fatal postulate assumed by Sprengel, but cross-fertilization a fact which, singularly enough, the latter's own pages proved without his suspicion.
Darwin thus foretold the precise manner of the cross-fertilization of Habenaria mascula, and also the insect agent, simply by the structural prophecy of the flower itself. Suppose, for example, an unknown orchid blossom to be placed in our hands. Its nectary tube is five inches in length, and as slender as a knitting-needle. The nectar is secreted far within its lip.
I recalled their singular shape, and the two outstretched stamens protruding from their gaping corolla, and could distinctly see them as I sat in the carriage. I had never chanced to read of this flower in the literature of cross-fertilization, and murmuring, half aloud, "What pretty mystery is yours, my Collinsonia?" prepared to investigate.
In them the elongated stigma now hangs directly in his path, and comes in contact with the pollen on his back as the insect sips the nectar. Cross-fertilization is thus insured; and, moreover, cross-fertilization not only from a distinct flower, but from a separate cluster, or even a separate plant.
It is now quite possible, as Darwin demonstrated, to look upon a flower for the first time and from its structure foretell the method of its intended cross-fertilization; nay, more, possibly the kind, or even the species, of insect to which this cross-fertilization is intrusted. Let us look at our Arethusa.
Five years and hundreds of millions of treasure were consumed, and then the world moved in not in zones, as was the idea of Baron Albrecht, but heterogeneously, according to the democratic American programme. It was a vast and happy intermingling of nationalities that settled down in China in 1982 and the years that followed a tremendous and successful experiment in cross-fertilization.
If they can but muzzle the flanks of the bell-mare once in twenty-four hours, often stopping a jolt from the heels of this temperamental monster the mules appear morally refreshed for any fate. Miraculous toilers, sexless hybrids successful ventures into Nature's arcanum of cross-fertilization steady, humorous, wise, enduring, and homely unto pain! The bond of their whole organization is the bell.
Who can suppose that such a costly process as this, and that all the exquisite arrangements for cross-fertilization in hermaphrodite plants, do not subserve some most important purpose? How and why the union of two organisms, or generally of two very minute portions of them, should reenforce vitality, we do not know, and can hardly conjecture. But this must be the meaning of sexual reproduction.
In a paper of this kind it is of course possible only to hint at a few representative examples of floral mechanisms, but these would be indeed incomplete without a closing reference to that wonderful tribe of flowers with which the theory of cross-fertilization will ever be memorably associated. I have previously alluded to the absolute dependence of the red clover upon the bumblebee.
The weight of this objection is obvious; but our ignorance of the conditions of fertility and sterility, the want of carefully conducted experiments extending over long series of years, and the strange anomalies presented by the results of the cross-fertilization of many plants, should all, as Mr. Darwin has urged, be taken into account in considering it. The eighth and last stands as follows:
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