SCIENCE SIFTINGS

New Zealand Tablet, 30 May 1918, Page 46

SCIENCE SIFTINGS

By “Volt.”

Migratory Trees. To an American contemporary we are indebted lor the recalling of the fact that as the early history of man was largely that of his migrations, certain investigators have found that the same is true of trees. When these are content to stay quietly at home, they go on reproducing in the same old image for generations. But as soon as individuals or groups take to travel they undergo marvellous-changes in the land of their adoption. The tiny dogwood, scarcely six inches tall in Alaska, becomes a 60-foot giant in Texas and Florida. In the Far North the honey locust is little more than a shrub; in the southern United States it is found as a medium-sized tree, well defended by thorns and prickles : in the still more luxurious climate of South America it develops into an immense structure bristling everywhere with vegetable spears. It must not be imagined that these tree movements are things of the past. In many parts of the country second and third growth timber is entirely unrelated to the original trees. The Catskill Mountains, when first visited by white men, were largely covered with spruce and hemlock. Such areas as have been cut over have nearly always been taken possession of by beech, apple, and birch . and of late years it has been noticed that poplars and aspens show a strong disposition to grow up in abandoned clearings. Another case, and one in which the hand of man is hardly to be seen assisting the transformation, is that of the wild red cherry, which within a -generation has spread from the eastern to the western Stales. Just how do trees travel? It would be an awe-inspiring spectacle to sse a great forest striding across the country, but except in the case of Macbeth s Birnam Wood, this has not been recorded as having taken place. They prefer to travel in embryo, tiansporting future forests halfway around the globe by means of tiny fruits and seeds light enough to soar through the air or float upon the water. An through the summer they devote their energies to maturing seeds and providing them with some sort of flying apparatus. Ihe seeds of the ash have paper-like wings. Those of the elms and maples are equipped with membranes as gauzy and delicate as those of a dragon fly. V illow, poplar, and catalpa seeds are attached to tiny balloons. Hop seeds have a kite-like appendage. The eveigieen trees and the birches produce winged seeds. The alders, tulips, and ashes send forth winged boxes —single seeds occupying matured pistils. The parachuted seeds of the pine are given an encouraging push into the world with the bursting of the cone. The exploding pods of witch hazel and wistaria fairly hurl their children out upon the. breeze. In the modest back-garden of the present writer, in Dublin, two promising ash trees are now growing, the seeds of which were never planted by mortal hands—they simply planted themselves.