How Trees Are Multiplied

HOW TREES ARE MULTIPLIED. Nature begrudges man all the land he has cleared of forests. and if he relaxes his vigilance—lets a field lie fallow a year or two— the forest begins to encroach, and takes it back. Every year trees flower and fruit, and young saplings come up wherever there is room and a chance in the woods. But here there is crowding and struggling even among the large trees, and the saplings die unless they can live under the shade of larger trees.

I. The Natural Way

The fortunate trees are those with abundant seeds, so light or so winged that they can sail off on the winds and fall in new places less crowded than the forest. The birches have such seeds—little heart-shaped discs with thin, papery webs on their edges all around. The pencil-like cones are packed with hundreds of these seeds, and the trees hang full of cones. What wonder, then, that birches so often follow in the wake of the lumbermen in New England woods. Pines and the other narrow-leaved evergreens are known by their cones. Have you ever shaken or beaten the seeds out of an opening cone of white pine? This is a typical conifer. The heavy brown seed has a wing by which the wind carries it. That very field now grown up to birches was once covered with virgin forests of pine. The neighbouring woods scatter pine seeds with birch and many other kinds. The birch gets the start. but in a few years you will see the little pines coming up in the shade of the birches. The "nurse trees" are short lived; they give way in time, and a pine forest follows the brief sway of the birches.

Why does poplar follow pine woods in many places? Note the poplar trees in early June. They are discharging seeds from long strings of green beads, burst open and turning brown. A puff of cottony substance, light as down, encloses each minute seed. There are millions on every tree. Wafted forth, these seeds lodge all over the neighbourhood. The cleared ground offers an opportunity. They spring up vigorously—a poplar forest. But under them are other slower, longer-lived trees loving the shade in their first years, but prepared to replace their poplar nurses in due season.

Look at the thin, round disc of the elm seed and you will see how the trees cater to their distributing friend, the wind.

How copiously the tree sheds its seeds in early summer! Notice the young elms that come up about the neighbourhood, if Nature is let alone. Observe the keen-pointed, winged dart an ash tree bears. What a burden of seeds one tree yields! Watch the tree on a windy day in October and on into winter. Study the winged key of the maples, the catalpa's thousands of thin, papery seeds in its hundreds of long pods that the wintry breezes shake and loosen and scatter every year. How much the willows' fuzzy seeds look like the poplars'—for willows' and poplars are own cousins! How different is the wing on the basswood's cluster of woody balls. The wind whirls them abroad and basswoods come up unexpectedly here and there. Sycamores bang their balls, and every loosened seed sails away on its own hairy parachute. The abundant ailanthus seed is balanced on a tipsy raft, that the wind carries long distances. The hornbeam seed sails in a shallop. The hop hornbeam seed is shut into an inflated balloon. The wind is the staunch ally of the forest in its policy of expansion.

So are the birds. The trees with fleshy fruits depend upon them. All the berries with small seeds, the sassafras, haws, Juneberries, hackberries, dogwoods, mountain ash, hollies and the cedars are in this group; cherries, too, and apples are dis tributed by birds to some extent. The larger fruits must wait for the larger creatures of the woods; they carry off the plums for the flesh and thin nut-like pits. There are the acorns and nuts that fall heavily, rolling down hillsides, if the parent tree is on the slope, but lodging soon, and waiting for squirrels and their kin to come and carry them off. The animals are selfish in this hoarding of nuts. They do not mean to leave one. But those that are hidden in the runways and not eaten, after all, sprout the next spring, and so the old nut tree is parent to scattered offspring, as well as to many that come up under its own shadow. The locusts their pods abroad to go careening over snow banks in winter, and so to break open at length and spill their flinty seeds. The witch hazel bursts open its woody pods in October and the seeds are shot out like bullets from a gun.