Arbor Day Leaves | Page 5

is a
beautiful contrivance also in connection with these pores, by which
they are closed when the air around is dry and the evaporation of the
water from the leaves would be so rapid as to be harmful to the tree,
and are opened when the surrounding atmosphere is moist.
The green color of the leaves is owing to the presence in the cells of
minute green grains or granules, called chlorophyll, which means
leaf-green, and these granules are indispensable to the carrying on of
the important work which takes place in the leaves. They are more
numerous and also packed more closely together near the upper surface
of the leaf than they are near the lower. It is because of this that the
upper surface is of a deeper green than the lower.
Such, then, is the laboratory of the leaf, the place where certain
inorganic, lifeless substances such as water, lime, sulphur, potash, and
phosphorus are transformed and converted into living and organic
vegetable matter, and from which this is sent forth to build up every
part of the tree from deepest root to topmost sprig. It is in the leaves
also that all the food of man and all other animals is prepared, for if any
do not feed upon vegetable substances directly but upon flesh, that
flesh nevertheless has been made only as vegetable food has been eaten
to form it. It is, as the Bible says, "The tree of the field is man's life."
But let us consider a little further the work of the leaves. The tree is
made up almost wholly of oxygen, hydrogen, and carbon. It is easy to
see where the oxygen and hydrogen are obtained, for they are the two
elements which compose water, and that, we have seen, the roots are
absorbing from the ground all the while and sending through the body
of the tree into the leaves. But where does the carbon come from? A
little examination will show.

The atmosphere is composed of several gases, mainly of oxygen and
nitrogen. Besides these, however, it contains a small portion of
carbonic acid, that is, carbon chemically united with oxygen. The
carbonic acid is of no use to us directly, and in any but very minute
quantities is harmful; but the carbon in it, if it can be separated from the
oxygen, is just what the tree and every plant wants. And now the work
of separating the carbon from the oxygen is precisely that which is
done in the wonderful laboratory of the leaf. Under the magic touch of
the sun, the carbonic acid of the atmosphere which has entered the leaf
through the breathing pores or stomates and is circulating through the
air-passages and cells, is decomposed, that is, taken to pieces; the
oxygen is poured out into the air along with the watery vapor of the
crude sap, while the carbon is combined with the elements of water and
other substances which we have mentioned, to form the elaborated sap
or plant-material which is now ready to be carried from the leaves to all
parts of the plant or tree, to nourish it and continue its growth. Such is
the important and wonderful work of the leaf, the tender, delicate leaf,
which we crumple so easily in our fingers. It builds up, atom by atom,
the tree and the great forests which beautify the world and provide for
us a thousand comforts and conveniences. Our houses and the furniture
in them, our boats and ships, the cars in which we fly so swiftly, the
many beautiful and useful things which are manufactured from wood of
various kinds, all these, by the help of the sun, are furnished us by the
tiny leaves of the trees.
BRYANT, THE POET OF TREES.
"It is pleasant," as Mr. George W. Curtis has said, "to remember, on
Arbor Day, that Bryant, our oldest American poet and the father of our
American literature, is especially the poet of trees. He grew up among
the solitary hills of western Massachusetts, where the woods were his
nursery and the trees his earliest comrades. The solemnity of the forest
breathes through all his verse, and he had always, even in the city, a
grave, rustic air, as of a man who heard the babbling brooks and to
whom the trees told their secrets."
His "Forest Hymn" is familiar to many, but it cannot be too familiar. It

would be well if teachers would encourage their pupils to commit the
whole, or portions of it, at least, to memory. Let it be made a reading
lesson, but, in making it such, let pains be taken to point out its
felicities of expression, its beautiful moral tone and lofty sentiment, and
its wise counsels for life and