Through all the millions of years during which the evolution of modern forms of life has been going on, then as now, trees must have entered prominently into the environment and lives of the terrestrial animals. Ages ago, long before snakes and four-toed horses were even foreshadowed, and before the first bird-like creatures had appeared, winged reptile-dragons flew about, doubtless roosting or perching on the Triassic and Jurassic trees. Perhaps the very pieces of coal which are burned in our furnaces once bent and swayed under the weight of these bulky animals. Something like six millions of years ago, long-tailed, fluttering birds appeared, with lizard-like claws at the bend of their wings and with jaws filled with teeth. These creatures were certainly arboreal, spending most of their time among the branches of trees. So large were certain great sloth-like creatures that they uprooted the trees bodily, in order to feed on their succulent leaves, sometimes bending their trunks down until their branches were within reach. On a walk through the woods and fields to-day, how seldom do we find a dead insect! When sick and dying, nine out of ten are snapped up by frog, lizard, or bird; the few which die a natural death seeming to disintegrate into mould within a very short space of time. There is, however, one way in which, through the long, long thousands of centuries, insects have been preserved. The spicy resin which flowed from the ancient pines attracted hosts of insects, which, tempted by their hope of food, met their death--caught and slowly but surely enclosed by the viscid sap, each antenna and hair as perfect as when the insect was alive. Thus, in this strangely fortunate way, we may know and study the insects which, millions of years ago, fed on the flowers or bored into the bark of trees. We have found no way to improve on Nature in this respect, for to-day when we desire to mount a specimen permanently for microscopical work, we imbed it in Canada balsam. If suddenly the earth should be bereft of all trees, there would indeed be consternation and despair among many classes of animals. Although in the sea there are thousands of creatures, which, by their manner of life, are prohibited from ever passing the boundary line between land and water, yet many sea-worms, as for example the teredo, or ship-worm, are especially fashioned for living in and perhaps feeding on wood, in the shape of stray floating trees and branches, the bottoms of ships, and piles of wharves. Of course the two latter are supplied by man, but even before his time, floating trees at sea must have been plentiful enough to supply homes for the whole tribe of these creatures, unless they made their burrows in coral or shells.