THE CHANGING COLOUR OF THE AUTUMN WOODS All through the autumn, when the wonderful colours come in the forest leaves, we shall see the green of these leaves creeping back along the veins. The horse chestnut leaves tell a very interesting story. They turn brown first upon the edges. If we watch a single leaf for a whole week in September, we may see the green gradu ally draw in towards the central stem, and the brown papery borders widen, just as if some thing were squeezing and crowding the pulp of the leaf, inch by inch, back through the leaf stem into the twig. The last traces of green linger along the sides of the veins, and before it falls, even these leaf channels will be drained dry.
When the leaves of a sugar maple give up their pulp there are wonderful changes inside each leaf. A yellow liquid fills the cells where the green pulp used to be. Chemical changes in the mineral substances deposited in the leaf cells produce wonderful shades of red and yellow, Changing Colour of Autumn Woods 75 which glow where once the leaf was solid green. Iron is one of the minerals brought up in the soil water, left in the leaf, and changed to pro duce the bright red when the leaf mask of green is taken away.
The scarlet maple remembers its name in the autumn days. It puts on a cloak more brilliant perhaps than the sugar maple, which has a good deal of orange as well as red in its autumn foli age. The scarlet oak is amazingly brilliant; so is the sassafras and the sweet gum. The tupelo, or sour gum, also called the pepperidge, has foliage that is splashed and streaked with various shades of red and yellow. Each little leaf is so brilliantly polished that the tree's beauty and colour seem to be doubled by reflection. The sumachs of the roadside thickets wear foliage of scarlet, each leaf drooping away from the fruit pyramid which rises, a deeper crimson, on the end of each upright shoot. The foliage and the fruit together make a colour harmony that is dazzling, indeed.
In contrast with its umbrellas of red leaves are the scarlet berry clusters of the flowering dog wood. This tree has the habit of snuggling up
against the trunk of large forest trees and reach ing its white flowery arms out to us in spring. How wonderful they are, on the edge of the woods, with the green leaves of the larger trees making a background for their flowers! In the autumn the same surprise awaits us, when under a towering tree with yellow or russet foliage, the dogwood leaps up like a scarlet flame, against its dark background, holding straight out its plat formed branches of red leaves, tipped with ber ries, like rubies, set on the upturned twigs.
Often the trees are stripped by birds before the berries are ripe. It is in woods where the trees are numerous that we shall find the fruit reaching its perfection of ripeness and colour.
Among the trees that turn to purple in the autumn we may name the white oak and the ashes. Many oaks turn from green to russet, without showing any red or yellow. The lindens and the tulip trees and the beeches turn yellow; so do the poplars and willows, the hickories, and walnuts. Up and down the street you may see the yellow crowns of the silver and the Nor way maples, and on the lawns the white birches have also turned to gold. The deepest red is on the black and red oaks. The brightest red is on the scarlet oak.
It is not fair to charge Jack Frost with all the gay colours of the autumn woods. Perhaps I should say, rather, that he does not deserve all the credit people give him for painting the landscape with the sunset glories of the dying leaves. The cause is the ripening of the leaves themselves, as I have already explained. Frost may hasten the process, but if a heavy freeze comes in September, before the leaves have coloured, we lose our chance for autumn colour ing that year. The leaves drop as if scalded, and the trees lose their leaf pulp, which they had expected to withdraw and save for future use. A long dry autumn of warm days and mildly frosty nights produces the finest succes sion of colours.