Bees are by no means the only pollen-carriers employed by flowers.
A large number of blossoms entrust their fate, or rather the fate of their posterity, to the mercy of the wind. Others, which grow and blow in ponds or streams, confide their pollen messages to the water. Flowers which conduct their affairs after these methods need be at no special pains to please the insects, whose services they neither ask nor need. So "wind-fertilized" and "water-fertilized" blossoms have not bright colors, nor fragrance, nor nectar. But, on the other hand, they must produce enormous quantities of pollen to ensure enough for Nature's needs, after a large proportion has been blown or washed away.
The wind-fertilized flowers of the poplar shed so much pollen that it may be seen, on breezy spring days, blowing from the branches in light clouds. And at one time in the summer the floating pollen of the eel-grass, and of some other pond weeds, is spread in sheets over the surface of still water. It has been shed by those aquatic flowers which blow at the surface of the water. There are other aquatic blossoms which expand beneath the surface. Their pollen grains are of much the same weight, bulk for bulk, as the surrounding water, so that they will neither float nor sink, but will remain poised at about the level of the flower they seek. And the individual pollen grains of such blossoms are often long and narrow in form, so that they cut their way through the water, as does a modern ocean greyhound.
Wind-fertilized flowers are adapted in various ways to their chosen assistants, the breezes. They have, for the most part, enormously developed stigmas, which project in the form of tails or brushes. The pollen of such flowers is light and dry, that it may blow easily, and the brush-like stigmas are covered with points or hairs which catch it as it flies past.
But the pollen grains which are to be entrusted to insect messengers are often sticky or roughened all over with little points, so that they catch on the hairy bodies of their winged porters, and cling.
The interdependence between flowers and their guests has lasted for so many generations, that certain insects have modified their chosen blossoms somewhat, and the flowers, in their turn, have modified their messengers. Thus there have come so be hereditary friendships in the outdoor world, to strong and so enduring that Delphino, who gave the subject much study, has made a rough classification in which flowering plants are graded "according to the company they keep".
His "first class" are adapted for the larger bees. They have diurnal flowers, with colors and scents attractive to man also.
Flowers of the second class are the particular friends of the lesser bees, though they also show hospitality to many other small insects. "These flowers," says Delphino, rather disparagingly, "have quite incomprehensible attractions for their visitors".
The third class comprises the big-fly flowers. These are often in dull shades of yellow and red, and exhale an odor disagreeable to man and to bees.
Another category of flowers are adapted for fertilization by smaller flies and lay wait for these foolish visitors with traps and snares, as does our familiar "Jack-in-the-Pulpit".
There are a few native plants which use carrion and dung-flies as their messengers. The carrion-flower of New England thickets is one of these. They have a putrid smell, often very strong, and dull-colored or greenish blossoms.
Delphino's sixth class includes those plants which seek to snare the fancy and secure the services of beetles. These have large diurnal blossoms with striking colors, very abundant pollen, and nectar so placed that it is within easy reach. Among these beetle-flowers is the magnolia.
Next come the butterfly-flowers, with bright corollas, and with their nectar concealed at the base of a tube so long and narrow that only their chosen guests can reach and sip it. And in the eighth class Delphino places those flowers which seek to please twilight and nocturnal moths.
Some plants have become so dependent on the ministrations of insects that they are no longer able to set seed by aid of their own pollen. It lies upon the pistil as powerless to awaken life as if it were mere roadside dust. Some of the orchids go even further in their repudiation of the pollen which they themselves have produced. The pistil seems poisoned by it, and withers at its touch.
Many flowers have special devices for securing pollen from other blossoms and for avoiding the use of their own.
In a number of species the stamens ripen, open, and shed their store, while the pistil is yet too young to make use of any pollen grains it may receive. Then when the pistil is old enough to commence business, and asks for gold, the surrounding stamens are a bankrupt community, with none left to give. But "all things come at last to one who knows how to wait." Pollen will be wafted to the pistil by a summer breeze, or carried to it by a winged messenger - beetle, fly, wasp, moth, butterfly, humming-bird, or bee. But it will be pollen from another flower, and that is exactly what wise Mother Nature has been planning from the first.
So the insects which flit through our gardens are combining business with pleasure and doing important errands for the flowers. The flowers vie for their attentions with charming toilettes, and pay for their services with free lunches.
The iris, geranium, gladiolus, and salvia, which make their debut later in spring when there are many beauties in the field, must be gay if they would be observed. They must appear in costumes which "shout," as the French say.
But the crocus has not needed a bewilderingly splendid dress in order to secure attention, because she has scarcely a rival thus early in the season, and it is rather Hobson's choice with the bee.
Thus there is scarcely a single brilliant or conspicuous blossom among all the first begotten of the spring. The early wild flowers which we find in sheltered sunny hollows are white, or pale-yellow, or lilac, or delicate sea-shell pink. The spurred columbines, in their brilliant uniforms of red and gold, will not appear upon the rocks till May. They have but coward hearts, for all their martial colors, and dare not come out so long as Jack Frost and the North Wind prowl abroad.
But the Joans of Arc among the flowers, which lead summer's hosts and brave winter's last desperate onslaughts, look as tender and demure as Priscilla "the Mayflower of Plymouth".