Fall leaf

“ Trees which are called evergreen, as pines and evergreen-oak, are always deprived of a certain number of leaves at intervals, sufficient being left, however, to preserve their green appearance. The cause of the fall of the leaf in cold climates seems to be deficiency of light and heat in winter, which causes a cessation in the functions of the cells of the leaf. The fall is directly caused by the formation of a layer of tissue across the base of the leaf-stalk ”

“ The shadows of leaves fall upon their arms, as they spread the branches apart, but their shoulders are in the sun. The skin of their arms is like a blue mist, but their shoulders are white and glowing, as if the light fell not from above, but rose from under their skin. We watch the leaf which has fallen upon their shoulder, and it lies at the curve of their neck, and a drop of dew glistens upon it like a jewel. ”

“ Thus in the fall, because the sap flows downward in the tree, the fiber of the leaf’s stalk is gradually weakened, until the leaf by degrees loses its hold on the branch, and, because everything obeys the law of gravitation, falls to the ground. ”

“ Although with us it is in autumn that our shrubberies lose their beauty, we are not to suppose such is the case everywhere, or that the same tree drops its leaves simultaneously in all countries. Many trees lose their leaves in spring, and the approach of winter is but a secondary element, so to speak, in the complicated list of causes which seem to operate in the fall of the leaf. In some tropical countries the leaves fall during the dry season which answers to our summer. ”

“ The living part of the leaf built it for a house to live and do its work in; now the house is empty: the living part has run down into the bulb or the underground stem. The part of the leaf that is left soon falls to pieces, as any old 186abandoned house will do. It falls on the ground; the rain soaks it, and it crumbles apart. It changes into food for other plants. It is not lost; it is taken up by other plants and again built into good plant material.
So it is with the seed-pods; when the seeds fall out, the part that is left behind is not alive. ”

“ The winter months when the woody vegetation is practically fully exposed to the elements, are particularly severe in their effects. Leaf-fall, which is such a common sight as to arouse scarcely any interest, is the only device by which the great bulk of our forest trees survive, and only in the southern part of the region are there found such woody plants as the mountain laurel, rhododendron, American holly, and a few others which are evergreen but not cone-bearing ones, and are the only reminders of the truly evergreen forests of the tropics. ”

“ Instead of having leaves in bunches of five, it has them in clusters of three, and [337] the base of each cluster is inclosed by a scaly sheath which does not fall away as in the case of the white pine; neither does the little scale-like body upon the branch, in the axil of which the leaf-cluster is borne, fall away, but it may be found just below the leaf, and even on branches that are several years old. Sometimes a sheath is found with only two leaves. We shall want to know, too, how old the leaves are when they fall. Do they remain on the tree longer than the white pine leaves do? ”

“ These interesting changes do not take place in the same way that nature does her work in the colder climates—by the leaves falling off in the fall of the year and the buds coming in the spring. With these trees the old leaf remains until forced off the limb by the new bud. ”

“ Far from it, the leaf is a highly complex structure. On the upper surface are a certain number of scattered hairs, while in the bud these are often numerous, long, silky, and serve to protect the young leaf, but the greater number fall off soon after the leaf expands. ”

“ How to Tell a Leaf.—It is often difficult to distinguish compound leaves from leafy branches, and leaflets [78] from leaves. As a rule leaves can be distinguished by the following tests: (1) Leaves are temporary structures, sooner or later falling. (2) Usually buds are borne in their axils. (3) Leaves are usually borne at joints or nodes. (4) They arise on wood of the current year’s growth. (5) They have a more or less definite arrangement. When leaves fall, the twig that bore them remains; when leaflets fall, the main petiole or stalk that bore them also falls.
Fig. ”

“ Why do you suppose leaves fall? It is better that they should; the sooner they fall, the sooner they will be converted into leaf mould to feed other plants. So the plants have a way of gathering their ripe harvest of leaves. ”

“ Leaf viewed laterally in its expanded state. (From Darwin’s “Insectivorous Plants.”)
In other plants adaptive movements are well known. “Few phenomena have such a peculiar appearance as the movements which occur in the sensitive Oxalis when rain comes on. Not only do the leaflets on which the finest rain-drops fall fold together in a downward direction, but all the neighbouring ones perform the same movement, although they have not themselves been shaken by the impact of the falling drops. The movement is continued to the common leaf-stalk bearing the numerous leaflets. ”

“ Autumn was falling, but the pine
Seem'd as it mock'd all change; no sign
Of season on its leaf was seen,
The same dark gloom of changeless green.
But like the gorgeous Persian bands
'Mid the stern race of northern lands,
The chesnut boughs were bright with all
That gilds and mocks the autumn's fall. ”

“ In fact, a leaf is a layer of the precious cambium spread out on a framework of veins and covered [Pg 18] with a delicate, transparent skin—a sort of etherealized bark. What a vast quantity of leaf pulp is in the foliage of a large tree!
As summer wanes, and the upward tide of sap begins to fail, starch making in the leaf laboratories declines proportionately. Usually before midsummer the fresh green is dimmed. Dust and heat and insect injuries impair the leaf's capacity for work. The thrifty tree undertakes to withdraw the leaf pulp before winter comes. ”

“ Like whispering voices, the trembling leaves sing rejoicingly in the breeze and summer sunshine, and they tremble alike with agony when the equinoctial gale rends them from the parent stalk. The influences which pervade the whole, making up the sum of vital force, are disturbed by every movement throughout the system; a wound on a leaf is known to disturb the whole, and an injury inflicted on the trunk interferes with the processes which are the functions of every individual leaf. ”

“ Something heavy came now, and pressed so hard that the seed came near being destroyed; but the leaf, weak though it was, protected it.
It was a human foot which walked along over the ground, and pressed the downy seed into the earth. When the foot was withdrawn, the earth fell, and filled the little pit it had made.
The cold came, and the snow fell several feet deep; but the seed lay quietly down there, waiting for warmth and light. When the spring came, and the snow melted away, the plant shot up out of the earth.
There was a little gray cottage beside which it grew up. ”

“ Now, imagine rain-drops falling on this plot of ground and sinking into the earth. On every side they will find rootlets thirsting to drink them in, and they will be sucked up as if by tiny sponges, and drawn into the plants, and up the stems to the leaves. Here, as we shall see in Lecture VII., they are worked up into food for the plant, and only if the leaf has more water than it needs, some drops may escape at the tiny openings under the leaf, and be drawn up again by the sun-waves as invisible vapour into the air. ”

“ Frost had already done its work upon the embrowned forests, and leaf by leaf the withered foliage had dropped away or been swept in clouds before the autumnal winds. Feebler and feebler grew, daily, the sun's planting rays, colder the air, and more cheerless the aspect of nature. ”

“ Others have nearly the richness of color, others again show nearly the elegance of leaf form, but no one tree rivals completely the sweet-gum at the time when the autumn chill has driven out all the paleness in its leaf spectrum, leaving only the warm crimson that seems for awhile to defy further attacks of frost. ”

“ The falling of the leaf is not an accident, nor is it dependent upon the wind; when the time comes, the leaves go down, wind or no wind, though doubtless the wind helps them. When they are fully ripe, the leaves let go! The cells that connect the leaf stem with the branch shrivel and shrink until the leaf is entirely separated from the parent plant; when this happens, the leaf falls. The ripe leaf is less juicy 189than the young leaf; its juices have departed and left the stiff, lifeless framework and the hardened skin, with the emptied cells beneath, to find their way to the earth. ”

“ It is a mistake to believe that the frost makes these brilliant colors: they are caused by the natural old age and death of the leaf, and [427] where is there to be found old age and death more beautiful? When the leaf turns yellow or red it is making ready to depart from the tree; a thin corky layer is being developed between its petiole and the twig, and when this is finally accomplished the leaf drops from its own weight, from the touch of the lightest breeze, or from a frost on a cold night. ”

“ The diminished light and heat of the shortening days is at the root of this derangement of the leaf’s vigour: but the latent process (as Bacon would have said) which develops itself from the very unfolding of the leaf till it drops from the tree, and acts in subordination to the above causes, is a problem physiology cannot easily explain. However, winter, with its high winds, frosts, and sapping rain, soon practically decides the question, by removing the decaying leaf. ”

“ The foliage glistens with a strange dew, that all day long drips on to the ground below, nurturing a rank growth of grasses, which shoot up in places so high that their spikes of fierce blood-fed green show far up among the deep-tinted foliage of the terrible tree, and, like a jealous body-guard, keep concealed the fearful secret of the charnel-house within, and draw round the black roots of the murderous plant a decent screen of living green. ”

“ But the quantity of leaves which annually falls has also much influence upon the extent to which the soil is capable of being improved by any given species of tree, as well as the degree of rapidity with which those leaves, under ordinary circumstances, undergo decay. The broad membranous leaf of the beech and oak decay more quickly than the needle-shaped leaves of the pine tribes, and this circumstance may assist in rendering the larch more valuable as a permanent improver. ”

“ Every year there forms, in the central top of the tree, a new leaf, which, closed like a fan, and defended by a downy, fawn-coloured covering, shoots up vertically to a height of ten feet, before it, expanding, droops gracefully, and assumes its place among its elder brethren; and as the imperative rule pervades all nature, that, in course of time, the eldest must give place unto their juniors, the senior lowest leaf annually falls withered to the ground, yet leaving a memento of its existence in a distinct ring or scar upon the parent trunk. ”

“ For when a leaf has a thin skin and a great many mouths, its water leaks away very quickly. And if many such leaves should remain upon a plant into the winter, might it not happen that they would let off all its water at a time when its roots could not find any more in the frozen ground? And thus might not the leaves kill the plant by draining it quite dry?
So you can see why it is well for most plants to shed their leaves before winter comes on and the root’s drinking water is turned into ice. ”

“ There was all the time in the world. He didn't squeeze the trigger until he had a perfect right-between-the-eyes bead, then he squeezed it ever so lightly. There was the sharp sound of the report, and then the small body falling swiftly, bouncing and glancing off limbs, tumbling over and over, making a rustling thump in the dry leaves at the tree's base. ”

“ So fed, this leaf expands, and remains on the stem all summer. The nursing leaves die when the aerial leaves have taken their food away, and then the first stage of oak hood has begun. It has subterranean and superterranean organs, the former finding plant-food in the earth, and the latter gathering it in the air, the sunlight, and the storm. ”

“ At least two visits should be made to the woods during the autumn months, one when the leaves of the trees begin to colour and another when the leaves have fallen. Consider the preparation made for winter in the woods and fields, the use of dead leaves in the woods as a protection to forest vegetation and as soil-making material. Bring [Pg 110] back samples of leaves and of leaf mould or humus for class-room observation. Note the effect of frost in hastening the falling of leaves—frost does not give the brilliant hues to leaves, as many people think. ”

“ No doubt, because it lives in places where the hot dust falls thick on the leaves at times, and if it did not have some trick of shaking it off, the leaf would be choked and bent so that the tree could scarcely breathe; for the leaves are the lungs of the trees. ”

“ When it strikes against a support, such as a stem or branch of a neighboring plant, the motion is arrested at the contact, but continues at the growing apex beyond, and this apex is thus made to wind spirally around the supporting body.
469. Leaf-movements are all but universal. The presentation by most leaves of their upper surface to the light, from whatever direction that may come, is an instance; for when turned upside down they twist or bend round on the stalk to recover this normal position. ”