Ingenious devices are resorted to in order to secure these desirable results. Many flowers make themselves useful to the insect world by secreting somewhere within their dainty cups little glands of honey, or, more properly speaking, nectar, for honey is the result of the bees' work. This nectar is highly prized by the insects and is, in many cases, the only object which attracts them to the flowers, although sometimes the pollen, which Darwin believes to have been the only inducement offered formerly, is sought as well.
But of course this nectar fails to induce visits unless the bee's attention is first attracted to the blossom, and it is tempted to explore the premises; and we now observe the interesting fact that those flowers which depend upon insect-agency for their pollen, usually advertise their whereabouts by wearing bright colors or by exhaling fragrance. It will also be noticed that a flower sufficiently conspicuous to arrest attention by its appearance alone is rarely fragrant.
When, attracted by either of these significant characteristics, - color or fragrance, - the bee alights upon the blossom, it is sometimes guided to the very spot where the nectar lies hidden by markings of some vivid color. Thrusting its head into the heart of the flower for the purpose of extracting the secreted treasure, it unconsciously strikes the stamens with sufficient force to cause them to powder its body with pollen. Soon it flies away to another plant of the same kind, where, in repeating the process just described, it unwittingly brushes some of the pollen from the first blossom upon the pistil of the second, where it helps to make new seeds. Thus these busy bees which hum so restlessly through the long summer days are working better than they know and are accomplishing more important feats than the mere honey-making which we usually associate with their ceaseless activity.
Those flowers which are dependent upon night-flying insects for their pollen, contrive to make themselves noticeable by wearing white or pale yellow, - red, blue, and pink being with difficulty detected in the darkness. They, too, frequently indicate their presence by exhaling perfume, which in many cases increases in intensity as the night falls, and a clue to their whereabouts becomes momentarily more necessary. This fact partially accounts for the large proportion of fragrant white flowers. Darwin found that the proportion of sweet-scented white flowers to sweet-scented red ones was 14.6 per cent, of white to 8.2 of red.
We notice also that some of these night-fertilized flowers close during the day, thus insuring themselves against the visits of insects which might rob them of their nectar or pollen, and yet be unfitted by the shape of their bodies to accomplish their fertilization. On the other hand, many blossoms which are dependent upon the sun-loving bees close at night, securing the same advantage.
Then there are flowers which close in the shade, others at the approach of a storm, thus protecting their pollen and nectar from the dissolving rain; others at the same time every day. Linnaeus invented a famous "flower-clock," which indicated the hours of the day by the closing of different flowers. This habit of closing has been called the "sleep of flowers."
There is one far from pleasing class of flowers which entices insect-visitors, - not by attractive colors and alluring fragrance - but "by deceiving flies through their resemblance to putrid meat - imitating the lurid appearance as well as the noisome smell of carrion."* Our common carrion flower, which covers the thickets so profusely in early summer that Thoreau complained that every bush and copse near the river emitted an odor which led one to imagine that all the dead dogs in the neighborhood had drifted to its shore, is probably an example of this class, without lurid color, but certainly with a sufficiently noisome smell! Yet this foul odor seems to answer the plant's purpose as well as their delicious aroma does that of more refined blossoms, if the numberless small flies which it manages to attract are fitted to successfully transmit its pollen.
* Grant Allen.
Certain flowers are obviously adapted to the visits of insects by their irregular forms. The fringed or otherwise conspicuous lip and long nectar-bearing spur of many orchids point to their probable dependence upon insect-agency for perpetuation; while the papilionaceous blossoms of the Pulse family also betray interesting adaptations for cross-fertilization by the same means. Indeed it is believed that irregularity of form is rarely conspicuous in a blossom that is not visited by insects.
The position of a nodding flower, like the harebell, protects its pollen and nectar from the rain and dew; while the hairs in the throat of many blossoms answer the same purpose and exclude useless insects as well.
Another class of flowers which calls for special mention is that which is dependent upon the wind for its pollen. It is interesting to observe that this group expends little effort in useless adornment. "The wind bloweth where it listeth" and takes no note of form or color. So here we find those Wan flowers without a name, which, unheeded, line the way-side. The common plantain of the country dooryard, from whose long tremulous stamens the light, dry pollen is easily blown, is a familiar example of this usually ignored class. Darwin first observed, that "when a flower is fertilized by the wind it never has a gayly colored corolla." Fragrance and nectar as well are usually denied these sombre blossoms. Such is the occasional economy of that at times most reckless of all spendthrifts - nature !
Some plants - certain violets and the jewel-weeds among others - bear small inconspicuous blossoms which depend upon no outside agency for fertilization. These never open, thus effectually guarding their pollen from the possibility of being blown away by the wind, dissolved by the rain, or stolen by insects. They are called cleistogamous flowers.
Nature's clever devices for securing a wide dispersion of seeds have been already hinted at. One is tempted to dwell at length upon the ingenious mechanism of the elastically bursting capsules of one species, and the deft adjustment of the silky sails which waft the seeds of others; on the barbed fruits which have pressed the most unwilling into their prickly service, and the bright berries which so temptingly invite the hungry winter birds to peck at them till their precious contents are released, or to devour them, digesting only the pulpy covering and allowing the seeds to escape uninjured into the earth at some conveniently remote spot.
Then one would like to pause long enough to note the slow movements of the climbing plants and the uncanny ways of the insect-devourers. At our very feet lie wonders for whose elucidation a lifetime would be far too short. Yet if we study for ourselves the mysteries of the flowers, and, when daunted, seek their interpretation in those devoted students who have made this task part of their life-work, we may hope finally to attain at least a partial insight into those charmed lives which find tongues in trees, books in the running brooks, Sermons in stones, and good in everything.