Chapter XXXVIII Importance of Bees to the Fructification of Flowers
Honey is regarded by modern naturalists as of no other use to plants but to allure insects, which, by visiting the nectaries of their flowers to procure it, become instrumental to their fertilization, either by scattering the dust of the stamens upon the stigmata of the same flower, or by carrying it from those which produce only male blossoms to those that bear female ones, and thereby rendering the latter fertile.
No class of insects renders so much service in this way as bees; they have however been accused of injuring vegetables, in three ways: 1st, by purloining for their combs the wax which defends the prolific dust of the anthers from rain; 2ndly, by carrying off the dust itself, as food for their young larvæ; and 3dly, by devouring the honey of the nectaries, intended to nourish the vegetable organs of fructificationAF.
AF Darwin’s Phytologia.
In defence of his insect protegées, Dr. Evans has observed:
“First, That the proportion of wax collected from the anthers is probably very trifling, it being so readily and abundantly obtainable from honey.
“Secondly, That for any depredations committed on the farina, they amply compensate, by their inadvertent yet providential conveyance of it, on their limbs and corslets, to the female organs of monoecious or dioecious plants; whose impregnation must otherwise have depended on the uncertain winds. This is exemplified in the practice of our gardeners, who in early spring, before they dare expose their hotbeds to the open air, and consequently to the access of insects, insure the fertility of the cucumbers and melons, by shaking a male blossom over each female flower. For the same purpose, and with the same success, a gentleman in Shropshire substitutes a male blossom, in place of the female one, at the top of his embryo cucumber, which instantly adheres, and falls off in due time. To the same kind intrusion of insects we owe the numberless new sorts of esculents and endless varieties of flowers in the parterre:
‘Where Beauty plays
Her idle freaks; from family diffus’d
To family, as flies the father dust
The varied colours run.’
Thomson.
“Thirdly, That in a great many instances, the honey-cups are completely beyond the reach of the fructifying organs, and cannot possibly be subservient to their use. Hence Sir J. E. Smith believes the honey to be intended, by its scent, to allure these venial panders to the flowers, and thereby shows how highly he estimates their value to vegetation. See his Introduction to Botany. In the same work, the author observes that Sprengel has ingeniously demonstrated, in some hundreds of instances, how the corolla serves as an attraction to insects, indicating by various marks, sometimes perhaps by its scent, where they may find honey, and accommodating them with a convenient resting-place or shelter while they extract it. This elegant and ingenious theory receives confirmation from almost every flower we examine. Proud man is disposed to think that
‘Full many a flower is born to blush unseen,’
because he has not deigned to explore it; but we find that even the beauties of the most sequestered wilderness are not made in vain. They have myriads of admirers, attracted by their charms, and rewarded by their treasures, which would be as useless as the gold of a miser, to the plant itself, were they not the means of bringing insects about it.”
Thus the bee, by settling upon and collecting honey from a thousand different flowers, is thereby assisting the great purpose of vegetable reproduction, at the same time that the loads she carries home enable her to construct receptacles for the reproduction of her own race.
“For the due fertilization of the common Barberry, it is necessary that its irritable stamens should be brought into contact with the pistil, by the application of some stimulus to the base of the filament; but this would never take place were not insects attracted, by the melliferous glands of the flower, to insinuate themselves amongst the filaments, and thus, while seeking their own food, unknowingly to fulfil the intentions of Nature in another department.” In some cases the agency of the hive-bee is inadequate to produce the required end; in these the humble-bee is the operator: these alone, as Sprengel has observed, are strong enough for instance, to force their way beneath the style-flag of the Iris Xiphium, which in consequence is often barren. Other insects besides bees are instrumental in producing the same ends; indeed they are necessary instruments: and hence according to the same naturalist, in some places, where the particular insect required is not to be met with, no fruit is formed upon the plant which is usually visited by it, where it is indigenous; for he supposes that some plants have particular insects appropriated to them. The American Aristolochia Sipho, though it flowers plentifully, never forms fruit in our gardens, probably for the reason just assigned. The Date Palm affords a striking instance of the necessity of extraneous intervention to perfect fructification; male and female flowers are borne on separate trees, and unless the two sorts be in the neighbourhood of each other, the fruit has no kernel and is not proper for food. There was a tree of this kind, bearing female flowers, at Berlin, for the fructification of which, a branch, with male flowers upon it, was once sent by post from Leipsic, (20 German miles,) and being suspended over some of the pistils, the tree afterwards yielded fruit and seed in abundance. Professor Willdenow has stated a very curious circumstance, concerning the Aristolochia Clematitis. He observes that the stamens and pistils of the flower are inclosed in its globular base, the anthers being under the stigma, which thereby requires the intervention of an insect, to convey the pollen to it. The Tipula pennicornis accomplishes this object; it enters the flower by its tubular part, which is thickly lined with inflected hairs, so as readily to admit the fly, but totally to prevent its release, till by the fading of the corolla the hairs have fallen flat against its sides. Hence the insect in struggling to effect its escape, brushes off the pollen and applies it to the stigma, thereby accomplishing the fertilization of the flower.