And so the plants which entrust their future to the wind have, on the whole, a wider geographical range. But in pollen-sending, as in some other undertakings, newer methods make for economy, and the old way of doing things is wasteful. The Coniferae have to produce so much pollen that there shall still be enough for all needs after a great quantity of the precious dust has been carried wide of its destination by vagrant winds.
So when the cone-bearing trees blossom, in May or June, their blown pollen is everywhere. It covers the surfaces of still waters, in the neighborhood of evergreen woods. Whole bucketfuls of it have been swept off the decks of vessels sailing close to the coast of North America. One observer has seen the ground near St. Louis covered with pollen, as if sprinkled with sulphur, and there was good reason to believe that it had been transported from pine forests, 400 miles to the south. "Kerner has seen the snow-fields of the higher Alps similarly dusted," says Darwin, "and another naturalist found numerous pollen-grains of Coniferae adhering to sticky slides which had been sent to a height of over five hundred feet by means of kites. Curiously enough more was found in the higher levels of the atmosphere".
The pollen of the Coniferae is enabled to fly thus adventurously abroad because each grain is provided with two bladdery wings, so that its outline suggests one kind of a Chinese kite (Fig. 80).
Fig. 80. - Winged pollen of the fir.
This winged pollen comes out of little sacs, which grow sometimes in pairs, sometimes in clusters, on the lower surfaces of shield-shaped scales, which have been called "staminal leaves." They are regarded as foliage leaves, set aside and altered over for new and higher uses.
Cooperation which brings about great results in the physical as well as in the industrial world enables the staminal leaves of the pine to make a brave show. They grow in long, close tufts, each of which is regarded as a very simple and primitive staminate flower (Fig. 81).
These flowers in their turn are massed in clusters, which are borne near the tips of boughs and twigs, where the wind can have its will with them. By latter May they are golden and conspicuous, and their abundant pollen flies from them in light clouds.
The staminal leaf-clusters, or staminate flowers, of the hemlock are more difficult to find, for they are not much larger than grains of rice, and they grow on the under surfaces of the branches.
Fig. 8i. - Flowers of the Scotch pine (Pinus sylvestris).
a, Staminate flower; b, a single "staminal leaf'; c, pistillate flower; d, upper surface of a carpel showing the two attached ovules; e, lower surface of a carpel. (From the Vegetable World).
Those of the junipers and red cedars make their presence evident by giving a yellow tinge to the boughs which bear them, but they are so tiny and so hidden among the leaves that one wonders how even the wind is able to find them out.
By time these humble flowers are prepared to give their pollen to the breezes the pistillate blossoms are ready to turn it to good account.
The staminal leaf is a rudimentary affair, but its affinity is, if possible, more rudimentary still. In the heart of a freshly-opened pea-blossom there is already an extremely small, but perfectly formed, pod. Suppose we pluck away from the pea-flower its calyx, corolla, and stamens, till nothing but this tiny pod is left. Now if we split it we shall find within it a number of minute peas. If we pick off all these except two, the remnant, a naked and opened pod with two peas, will be equivalent to the "carpel" of most native cone-bearers.
The young cone is a community of carpels, each having its pair of attached ovules, and all arranged spirally about a woody axis. The very young "berry" of a red cedar or a juniper is a close ring of carpels enclosing a few ovules. And in both these cases the entire cluster is regarded as a single pistillate flower.
The ovule of the yew lives alone and is a "pistillate flower" all by itself. It is partly enveloped by small scales, and a little ring-shaped disk closely invests its base.
Among the red cedars, junipers, and yews some individuals bear pistillate flowers only, while others devote all their energies to the production of staminal leaves and pollen. But all other native evergreens produce both sorts of flower on the same tree, and they may frequently be seen on the self-same branch.
The ovule of a flower akin to the lily or the rose generally wears two coats. But the ovule of a cone-bearer has but a single coat, and at one point it presents a naked surface to the pollen.
Because their ovules are not enclosed in pistils the cone-bearers and their kin are known to systematic botany as "gymnosperms" (naked seeds). They are a last link in the chain which connects the flowerless and the flowering plants.
Naturalists assign the highest rank among flower-less plants to the club-mosses, and the selaginellas their nearest of kin.