Thus we see the four successive steps in progressive knowledge, from Grew in 1682, Linnæus, 1735, Sprengel, 1787, to Darwin, 1857-1858, and realize with astonishment that it has taken over one hundred and seventy-five years for humanity to learn this apparently simple lesson, which for untold centuries has been noised abroad on the murmuring wings of every bee in the meadow, and demonstrated in almost every flower.
This infinite field now open before him, Darwin began his investigations, and the whole world knows his triumphs. He has been followed by a host of disciples, to whom his books have come as an inspiration and ennobling impulse. Hildebrand, Delpino, Axell, Lubbock, and, latest and perhaps most conspicuous, Hermann Müller, to whom the American reader is especially referred. "The Fertilization of Flowers," by this most scholarly and indefatigable chronicler, presents the most complete compendium and bibliography of the literature on the subject that have yet appeared. Even to the unscientific reader it will prove full of revelations of this awe-inspiring interassociation and interdependence of the flower and the insect.
Many years ago the grangers of Australia determined to introduce our red clover into that country, the plant not being native there. They imported American seed, and sowed it, with the result of a crop luxuriant in foliage and bloom, but not a seed for future sowing! Why? Because the American bumblebee had not been consulted in the transaction. The clover and the bee are inseparable counterparts, and the plant refuses to become reconciled to the separation. Upon the introduction and naturalization of the American bumblebee, however, the transported clover became reconciled to its new habitat, and now flourishes in fruition as well as bloom.
Botany and entomology must henceforth go hand-in-hand. The flower must be considered as an embodied welcome to an insect affinity, and all sorts of courtesies prevail among them in the reception of their invited guests. The banquet awaits, but various singular ceremonies are enjoined between the cup and the lip, the stamens doing the hospitalities in time-honored forms of etiquette. Flora exacts no arbitrary customs. Each flower is a law unto itself. And how expressive, novel, and eccentric are these social customs! The garden salvia, for instance, slaps the burly bumblebee upon the back and marks him for her own as he is ushered in to the feast. The mountain-laurel welcomes the twilight moth with an impulsive multiple embrace. The desmodium and genesta celebrate their hospitality with a joke, as it were, letting their threshold fall beneath the feet of the caller, and startling him with an explosion and a cloud of yellow powder, suggesting the day pyrotechnics of the Chinese. The prickly-pear cactus encloses its buzzing visitor in a golden bower, from which he must emerge at the roof as dusty as a miller. The barberry, in similar vein, lays mischievous hold of the tongue of its sipping bee, and I fancy, in his early acquaintance, before he has learned its ways, gives him more of a welcome than he had bargained for. The evening primrose, with outstretched filaments, hangs a golden necklace about the welcome murmuring noctuid, while the various orchids excel in the ingenuity of their salutations. Here is one which presents a pair of tiny clubs to the sphinx-moth at its threshold, gluing them to its bulging eyes. Another attaches similar tokens to the tongues of butterflies, while the cypripedium speeds its parting guest with a sticking-plaster smeared all over its back. And so we might continue almost indefinitely. From the stand-point of frivolous human etiquette we smile, perhaps, at customs apparently so whimsical and unusual, forgetting that such a smile may partake somewhat of irreverence. For what are they all but the divinely imposed conditions of interassociation? say, rather, interdependence, between the flower and the insect, which is its ordained companion, its faithful messenger, often its sole sponsor-the meadows murmuring with an intricate and eloquent system of intercommunings beside which the most inextricable tangle of metropolitan electrical currents is not a circumstance. What a storied fabric were this murmurous tangle woven day by day, could each one of these insect messengers, like the spider, leave its visible trail behind it!
As a rule, these blossom ceremonies are of the briefest description. Occasionally, however, as in the cypripedium and in certain of the arums, or "jack-in-the-pulpit," and aristolochias, the welcome becomes somewhat aggressive, the guest being forcibly detained awhile after tea, or, as in the case of our milkweed, occasionally entrapped for life.
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From this companionable point of view let us now look again at the strange curved stamen of the sage. Why this peculiar formation of the long curved arm pivoted on its stalk? Considered in the abstract, it can have no possible meaning; but taken in association with the insect to which it is shaped, how perfect is its adaptation, how instantly intelligible it becomes! Every one is familiar with the sage of the country garden, its lavender flowers arranged in whorls in a long cluster at the tips of the stems. One of these flowers, a young one from the top of the cluster, is shown at A (Fig. 4), in section, the long thread-like pistil starting from the ovary, and curving upward beneath the arch of the flower, with its forked stigma barely protruding (B). There are two of the queer stamens, one on each side of the opening of the blossom, and situated as shown, their anthers concealed in the hood above, and only their lower extremity appears below, the minute growth near it being one of the rudiments of two former stamens which have become aborted. If we take a flower from the lower portion of the cluster (D), we find that the thread-like pistil has been elongated nearly a third of an inch, its forked stigma now hanging directly at the threshold of the flower. The object of this will be clearly demonstrated if we closely observe this bee upon the blossoms. He has now reached the top of the cluster among the younger blossoms. He creeps up the outstretched platform of the flower, and has barely thrust his head within its tube when down comes the pair of clappers on his back (C). Presently he backs out, bearing a generous dab of yellow pollen, which is further increased from each subsequent flower. He has now finished this cluster, and flies to the next, alighting as usual on the lowermost tier of bloom. 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. For in these older stigmatic flowers the anther as it comes down upon his back is seen to be withered, having shed its pollen several days since, the supply of pollen on the bee's body being sufficient to fertilize all the stigmas in the cluster, until a new supply is obtained from the pollen-bearing blossoms above. And thus he continues his rounds.