The connection between insects and the plant-world, and the mutual benefits they render, have long been known to man. While the one kingdom is almost entirely dependent on the other for sustenance, and this, not only as regards food, but for dwelling-places also: the organic, but (so far as we can judge) inanimate, one of the two, requires the aid of the animate for the continued reproduction of many of its members.

It would lead us too far from the subject of this book to enter at all fully into the question of the complete interaction of plant-life and insect-life. In dealing with the relations of bees to flowers we shall, therefore, confine our remarks almost entirely to the important part played by these creatures in the reproduction of certain kinds of plants.

It may, perhaps, be necessary, previously to entering on this subject, to say that in flowers we have organs analogous to, though widely differing from, those indicative of sex in the animal world. The functions, at least, are the same; and the combined action of the two sets is essential to the propagation of the race by seed. Unless pollen from the anthers is conveyed to the pistil, and, germinating there, imparts to the ovules vivifying nourishment, no seed will come to perfection, or will be capable of growing. While most flowers are hermaphrodite, i.e. produce both stamens (or anther-bearers) and pistils, it happens, in not a few instances, that certain flowers have anthers, and no pistils: while others, on the same plant, have pistils, but no anthers. Again, the antheriferous and pistiliferous flowers, in certain species, are found on different individual plants, so that, unless some agency were provided for the transference of the pollen, these species would inevitably die out. Now, the two means for this conveyance are the wind and insects. It is evident that the former can have only a very limited action, and would need for its effective service a great abundance of any particular flower, lest the fructifying grains should become the mere sport of the breezes, and fail to reach their all-important goal, and accomplish their all-needful function.

Moreover, in many cases, the position of the anthers in the flower entirely excludes the possibility of any currents of air assisting in the carrying of the pollen-dust to the pistil of the same or of different flowers. Hence there is a necessity for the intervention of insects; and that they may be induced to visit such flowers, and unconsciously effect the essential operation of fertilising them, nectar is secreted near the base of the stamens or the ovary, or in some position which will involve, in the gathering of it, the brushing off and conveying away of some of the pollen-grains. It is, indeed, a remarkable fact that fragrance and honey-bearing are scarcely ever associated with plants which can easily be wind-fertilised. Such flowers are, also, for the most part, inconspicuous; while those which need the agency of insects to aid in their reproduction are bright in colour, sweet in perfume, and more or less prolific in honey.

It must not be supposed, however, that even the hermaphrodite, or double-sexed, flowers are independent of the visits of bees and other insects. In all of them cross-fertilisation, as Darwin has abundantly proved,[10] is a most important factor in the continued vitality of any species, and cross-breeding gives an immense advantage in "the struggle for existence," where the conditions of life are not wholly favourable. Indeed, in many instances, special provision has been made by the Creator against self-fertilisation: in some cases, by the anthers and pistil coming to maturity, in the same flower, at different times; in others, by the placing of the stamens in such a position relatively to the stigma (or top of the pistil) that it is not possible for the pollen-grains of the one set of organs to fall on the surface of the other. It cannot but be interesting to give examples of these various facts, and so to show the marvellous and necessary connection between the two kingdoms of nature.

Firstly, then, as well-known instances of pistil-bearing and stamen-bearing flowers occurring separately on the same plant, we may mention cucumbers, melons, marrows, et hoc genus omne. Now, when these vegetables are grown under glass, whether in greenhouses or in pits, to which bees and other insects have little or no access, gardeners find it necessary themselves to apply the pollen-bearing portions of the one kind of flower to the pistil of the other. If this is neglected to be done, the fruit makes no progress, turns yellow, and dies. Where, however, the plants are grown in the open air, or are not so shut up as to exclude insects, they will be fertilised without the intervention of man; for bees of various kinds will certainly visit the flowers, and carry the life-giving dust where it is needed. In fact, we believe it might be asserted with confidence, that in all plants, where this separation of, what we may call, the sexes takes place, the flowers possess special attractiveness to the tenants of our hives; and it is well that this is the case, otherwise the continued existence of such plants would be seriously endangered.

As examples of diœcious genera, or those having pollen-bearing flowers on one plant and pistiliferous flowers on another, we may note the willows, the poplars, and the firs; and it is remarkable that these all are special favourites with bees. In the early spring, when breeding has been going on in the hives, and when the demands of the advancing larvæ require considerable supplies of pollen, the catkins of the willow are abundantly visited, and the diffusion of their fertilising powder is thus greatly promoted. The same may be said about the poplar, and, in all probability, the gathering of propolis from trees of the fir-tribe makes the bee the unconscious, but useful, instrument of carrying pollen from the catkins to the cones, though, from the abundance of the powder, and the openness of the scales of the cones r the wind is a sufficiently effective agent for its conveyance in this order of trees.

Passing next to cases in which the stamens and pistils of the same flower come to maturity at different times, so as to make cross-breeding a necessity, we may mention first some plants in which the pollen ripens before the stigma is ready to receive it. We have such a condition of things in the willow-herb, or epilobium tribe. The pretty pink blossoms of a large variety of this genus are to be found, in summer, along the banks of brooks and running ditches. We will confine our remarks to the species distinguished by its narrow leaves, and hence named angustifolium. When the flower has fully opened, the eight stamens spread out, and their anthers shed the pollen. Bees visit the blossoms, and getting dusted with the grains, carry these away to other flowers of the same kind. And here, in passing, we may recall the fact of bees keeping to one species of plant during the whole of any one journey from the hive. The importance of this can be now better appreciated, when its influence on the fructification of blossoms is observed. But to return, the pistil of the willow-herb remains, till the stamens have withered, curved round out of the way, and unable to receive any of their pollen. Then, after they are dead, it comes into such a position that it can take what pollen may be brought to it from younger flowers. For the conveyance of this it is dependent chiefly on bees, who do not fail to carry enough for the required purpose. In this way each blossom, by the agency of these insects, both gives and gets what is necessary for the continued life of the species; and without these unconsciously conferred benefits from insect life, no seeds of this kind of epilobium would mature.

Another instance, equally interesting, is seen in the well-known cineraria tribe. The plants of this genus belong to the composite order, in which what is usually called the blossom, consists of many flowers, grouped together on one head. In the example before us, there are nearly 200 thus aggregated. These florets separately open at different times, those of the outer circles coming before those nearer the centre. The pollen-tube of each is formed by five anthers, fastened together at their edges, and discharging their pollen into the space between them. At the lower part of this inclosure the pistil is growing, but is not in a condition to receive usefully the fertilising powder. It, however, as it advances, sweeps out, and carries up with it, the pollen-grains, so that they may be conveyed to other florets of the same or other blossoms, to effect their vitalising work. At length the pistil, with its brush on its summit, comes into view, but, even yet, is not sufficiently developed for fertilisation. In due course, however, the upper end splits, and exposes the surface of the stigma ready for the pollen, which must be brought from some other floret, and probably from some other blossom. Thus cross-breeding is effectually secured.

Another point for attaining this end is worthy of remark. The outer ring of florets is distinguished by long, coloured petals, which make up, in common parlance, the flower of the cineraria. These serve to render the composite head conspicuous, and attractive to insects. Some varieties, moreover, emit fragrant odours, and thus present further inducements for visitation. It is remarkable that, in these florets of the outer edge, the gay-coloured petals are developed at the expense of the anthers. Consequently, they produce no pollen, and their pistils have no brushes, as there would be no office for them to perform. The bright rays have accomplished their own special purpose, and the florets may well depend on others for pollen.

Now, as to the great importance of cross-fertilisation in this species, we may quote the experiments made by Dr. Darwin.[11] He says: "Two purple-flowered varieties (of cineraria) were placed under a net in the greenhouse, and four corymbs (or bunches of flowers) on each were repeatedly brushed with flowers from the other plant, so that their stigmas were well covered with each other's pollen. Two of the eight corymbs thus treated produced very few seeds, but the other six produced on an average 41.3 seeds per corymb, and these germinated well. The stigmas on four other corymbs on both plants were well smeared with pollen from the flowers on their own corymbs; these eight corymbs produced altogether ten extremely poor seeds, which proved incapable of germinating. I examined many flowers on both plants, and found the stigmas spontaneously covered with pollen; but they produced not a single seed. These plants were afterwards left uncovered in the same house, where many other cinerarias were in flower; and the flowers were frequently visited by bees. They then produced plenty of seed, but one of the two plants less than the other, as this species shows some tendency to be diœcious.

"The trial was repeated on another variety with white petals tipped with red. Many stigmas on two corymbs were covered with pollen from the foregoing purple variety, and these produced eleven and twenty-two seeds, which germinated well. A large number of the stigmas on several of the other corymbs were repeatedly smeared with pollen from their own corymb; but they yielded only five very poor seeds, which were incapable of germination. Therefore the above three plants, belonging to two varieties, though growing vigorously and fertile with pollen from either of the other two plants, were utterly sterile with pollen from other flowers on the same plant."

A condition similar to that described in the cineraria is found in the nasturtium (Tropœolum majus). In the young blossom may be observed the five stamens fully developed, while the stigma remains quite out of their reach. Later, when all the pollen is discharged from the anthers, the pistil throws up its style and stigma, now ready for fertilisation, which must be effected by the transfer of pollen from some other blossom of the same or another plant of the species. This transfer is effected, usually, by the bees.

Another example of this non-coincidence in the times of development of the stamens and pistil is found in the foxglove (Digitalis purpurea), but the fertilisation is effected by the larger humble-bees. The two upper and longer stamens shed their pollen before the two lower and shorter ones. This arrangement partly avoids the risk of self-fertilisation, while their position, which changes just when the anthers are ripe, enables them to smear the under side of any entering bee; while they also shed their pollen abundantly on the thickly-set hairs lining the mouth of the corolla. A second use is served by these hairs, viz., that of obstructing the entrance of the smaller kinds of bees, which could not so effectually fertilise the ovules. The larger sorts, in their raids upon the nectar, carry pollen from flower to flower, thus in the best manner bringing about the most desirable result of cross-breeding.

Passing now to plants in which the pistil develops earlier than the stamens, we may note the knotted figwort (Scrophularia nodosa). On making a section of a recently opened flower, the style, with its stigma, may be observed protruding just beyond the lip of the corolla, while the stamens are hiding away, as it were, in a little pouch below the entrance of the blossom. When fertilisation by pollen from another flower has taken place, the pistil droops and withers; while the anthers grow upwards to the mouth of the corolla, and present their nectar to the honey-seekers, for conveyance to other flowers of the species.

In the common sage (Salvia officinalis) we find a very remarkable contrivance, by means of which the anthers, through a sort of hinge-like connective, are brought down on the back of a bee entering the flower. The pollen thus discharged is carried by the insect to other blossoms, in which the place of the withered stamens has been occupied by the stigma now ready to receive the grains. Thus again inter-breeding is secured.

The next figure represents the very curious arrangement of the stamens in the Erica tetralix, or common heath. These, eight in number, are seen standing round the style, at about half its length. Each is held by a long filament (only one of which is shown in the figure), and is armed with a horn-like process. When the anthers are ripe, the pollen would escape from openings in their sides, were it not that the little slits abut on each other. When, however, a bee visits the flower, and thrusts up her proboscis, this strikes against one of the little horns, and pulls apart its anther from the rest. Pollen then drops on the bee's head, to be carried by it to other blossoms, which, while receiving a portion brought to them, in their turn give the bee a supply to carry to other flowers. It is a very salutary thing for the propagation of the heath that bees have such a strong liking for its nectar, and are thus induced to perform, albeit unconsciously, the process of fertilisation.

In the strawberry the stigmas are ripe long before the pollen is ready; and hence we understand why the Creator has arranged that the nectar of these blossoms should be so attractive to the bees, whose visits are so necessary for the development of the fruit. When fertilisation takes place, growth proceeds in the ordinary manner, and with results so satisfactory to mankind. Where pollen fails to fall on any of the multitudinous stigmas, we have a shrunken, hard, greenish mass. Any dish of strawberries will show where this has happened. It is said that to produce one perfect specimen of the fruit, from 100 to 300 separate fertilisations must be effected.

In the raspberry and blackberry again, each drupel, or little fleshy portion, of which very many make up one so-called berry, has had its own stigma, which an insect has visited; and hence again, we understand how it is that the flowers have been so largely endowed with nectar, as to entice the bees most freely to visit them.

In apple and pear blossoms we have other instances of the stigmas coming to maturity before the anthers; and, therefore, they require the intervention of bees for their fertilisation. Peaches, apricots, nectarines, plums, greengages, and, we might almost venture to assert, all our choicest and most valuable fruits, are dependent for their perfection upon the busy searchers after honey; and many a market-gardener would greatly increase his chances of good crops of fruit, were he to maintain a few stocks of bees in his orchards, and allow access for the active workers to his trees blossoming under glass-houses.

From the vegetable world we might adduce many other evidences of the marvellous interdependence of the two great kingdoms of organic nature. Enough, however, has been said to illustrate this point, and we trust that some of our readers may be led to further investigation in this field, which opens up such wonders, and such pleasurable surprises, for all who care to trace evidences of the Creator's infinite resources, wisdom, and care for all that He has made.

Everywhere, also, on earth may be seen at work the grand law of self-sacrifice for others' needs. Very many facts which we have detailed in the natural history of bees, illustrate this most thoroughly. We may, indeed, say that the life of a worker, who will neither have progeny of her own, nor see many of the race for whom she spends her powers, is one continued offering of herself for the welfare of the community. As the Latin poet says, Sic vos non vobis, mellificatis apes; and thus these unselfish toilers, beside teaching us many another lesson, seem to foreshadow, and to lead our thoughts to, the infinite gift of Him "who gave Himself for us" that we in and through Him might have life.

God has written tokens of His wisdom and love around us everywhere. None who reverently observe any of His works can fail to see His attributes embodied throughout all nature.