In February, too, the roads are no longer edged with dead white grass, but show the fresh green of wayside plants—cow-weed, nettle, dock, and cleavers.
The trees still stand naked, their leaf-buds waiting for a better season. I like to think of wintering plants not as being asleep, but rather as silent. They sing with all their green tongues when spring releases them from the cupboards (which we call buds) where she has kept them safe.
The service-tree is a hardy creature, for its buds are naked and unprotected, like Pampas Indians who are proud of sleeping uncovered, and of seeing, as they rise, their forms outlined in the hoar-frost. I have only recently noticed the purple tint of alder-buds; [5] and I am reminded of the character in Cranford, who needs Tennyson’s words “Black as ash-buds in March” to teach him the fact. Some trees show their flowers early. For instance, the hanging tassels of the hazel, from which the dusty pollen can be shaken out, and the tiny red tufts which are all the female flower has to show. The alder, too, has a brave crowd of lambs’ tails. The elm should flower about the middle of March, and its pink stamens make a pleasant sight. These plants are called anemophilous—that is, wind-loving, as though grateful to the wind for carrying their
pollen without payment. I can imagine that the plants employing insects to carry pollen from one to another feel superior to the wind-fertilised clan. We may fancy the duckweed (speaking of the pine) to say: “Of course, he is very big and of an ancient family, but for that very reason he is primitive in his habits. I know he boasts that he employs the winds of heaven as marriage priests, but we are served by the animal kingdom in our unions—and that, you must allow, is something to be proud of.” [6] But duckweeds grow so crowded together that they are probably fertilised, to a great extent, by contact with their neighbours, without aid from the animal kingdom. We may also imagine the duckweed reproving the pine for his extravagance in the matter of pollen production. This, however, is necessary, because the pollen being sown broadcast by the wind, it is a matter of chance whether or not a grain reaches the stigma of its own species, and the chance of its doing so is clearly increased by multiplying the number of pollen-grains produced. Enormous quantities of the precious dust are wasted by this prodigality. We read of pollen swept from the decks of ships, or coating with a yellow scum lakes hidden among Tyrolean pinewoods. Pollen is so largely dispersed in the air that it has been supposed to be a cause of hay-fever.
Blackley found, by means of a sticky plate, which
could be exposed and covered again, when raised high in the air on a kite, that pollen is dispersed to considerable altitudes. Wherever vegetable débris collects, pollen-grains may be found. Kerner found them, together with wind-borne seeds and scales of butterflies’ wings, sticking to the ice in remote Alpine glaciers.
Another characteristic of wind-borne pollen is dryness or dustiness; the grains are smooth, not sculptured like the pollen meant to be carried by insects; nor are they sticky or oily, as is often the case with entomophilous pollen. The advantage to the plan is obvious; the grains, from the absence of the burr-like quality, or of any other kind of adhesiveness, do not tend to hold together in clumps, but separate easily from one another, and float all the more easily. [7]
Several adaptations are found to favour the dispersal of the pollen. Wind-fertilised plants are generally tall; thus in Europe, at least, the commonest representatives of the class are shrubs or trees—witness the fir-trees, yew, juniper, oak, hazel, birch. And where the plants are lowly—e.g., grasses and sedges, and the plantains—the flowers are more or less raised up on the haulm. An exception must be made of some water-plants—e.g., the Potamogetons, where the flower-stalk is but slightly raised above the surface.
Wind-fertilised plants have many characteristics which favour the dispersal of the pollen. The grasses
have long pendent stamens, and versatile anthers, from which the pollen is easily shaken out by the wind. There are, of course, exceptions to these generalisations. Such plants as Hippuris and Salicornia have no particular adaptations: the filaments are short, and the plants themselves are not of sufficient height to be able to scatter forth their pollen efficiently by the mere bending of their stems. The need for exposure to the wind is shown in another way—namely, by the habit of the Cupuliferæ (oak, hazel, etc.), of flowering before the leaves appear; this not only favours the start of the pollen on its flight, but is probably still more useful in increasing its chance of reaching the stigma.