countless numbers of leaves which are developed through succeeding years, and by whose united labors a goodly tree is at last constructed, capable of withstanding the storms of the atmosphere, as the submarine structures reared by the coral insect resist the surges of the ocean.

It is therefore important to study carefully the organization and life-processes of the first true aerial leaf, or vegetable unit; for as its simple repetition constitutes the growth of the first year-which again must be regarded as a vegetable unit of a somewhat higher, more complex character, by simple repetition of which the entire tree itself is ultimately produced; so it is plain that a thorough knowledge of the physiology and organization of this first true aerial leaf must furnish a key not only to the growth of the first year, but of succeeding years, of which the tree is the solid and enduring monument.

Nothing is apparently more insignificant and feeble than our beech-tree at this period of its life. Look at the young, delicate leaf and stem of the phyton, or first plant, which does not even raise above the green blades of grass by which it is surrounded, thrown as it were on the charity of Nature! It has lost its nursing-leaves and is left to provide for itself, surrounded by innumerable dangers. It is at first a struggle for life against fearful odds. It may be eaten by cattle, or be crushed by a careless footstep; want of rain or too much moisture in the soil, excessively hot or severely cold weather, may permanently injure its structure and bring its life to an early and premature close.

But if the seed was planted in a good soil, and the conditions continue favorable, an impulsive energy will very soon be called forth which shall carry it over every obstacle. Yea, verily, it shall extract nutriment from the very tempest which would hurl it to destruction, and render its enemy subservient to the advancement of its upward and onward progress.

See how beautifully Providence has adapted the organization of the two extremities of the phyton, or first plant,

to the earth and atmosphere, the two sources from whence it must for the future draw its supplies of food. Its little root descends into the soil, and puts forth from its surface a number of fine, white, hairlike fibres, which are the instruments by means of which the plants absorb inwardly the subterranean nutrient material which surrounds them; its young stem ascends into the air, and the bark and fibre, which are arranged cylindrically in separate beds or layers in the stem, are spread out horizontally towards its summit, in the form of a flat green plate, or absorbent surface, called a leaf.

The bark, or cellular tissue of this leaf is penetrated by the fibrous portion of the stem, in the shape of veins and veinlets, which communicate freely with the roots in the soil, and thus act as conduits of the sap or nutritive material from one extremity of the plant to the other. In this manner the sap, brought from all parts of the plant, becomes, as it were, thoroughly spread out and aerated in the leaf. To facilitate the processes of evaporation and absorption, the leaf is provided with an epidermis, through the pores or openings of which the superfluous water of the sap is evaporated, and such gases absorbed from the atmosphere as are nutritious to the plant.

Hence, when fully developed, this leaf aerates the sap much more perfectly than the nursing-leaves; and as it is a true aerial leaf, it remains permanently attached to the stem or vegetable axis till the close of the vegetative seaThis leaf appears, in fact, to be formed in reference to the atmosphere.

son.

If we examine the gemmule, or young bud, situated just above the phyton, or first leaf, we shall find that the first leaf itself is now, in its turn, a nursing-leaf, and the parent of a numerous progeny of already partially-formed follicles. These, nourished by the sap elaborated in the first leaf, soon individually expand and separate from each other, little intervals of stem being formed between them. They now contribute individually to each other's support: the lower leaves aiding in the development of those that are above

them, and contributing also to the growth of that portion of the axis or stem which is beneath them, and to the increase of the number of the rootlets in the soil.

Each of these phytons or leaves developes also, more or less perfectly, its own gemmule or young bud, which, undoubtedly, corresponds to the gemmule or bud formed by the first leaf, the unfolding of which constitutes the growth of the first season. But these new buds never come to anything the first year, but retain their rudimentary condition through the winter months, and appear as projecting points on the outside of the shoot, after the leaves which formed them have dropped from the stem. The gemmule or bud formed by the first leaf, is the only one of the series which developes the first season.

As the heat and light of the sun decrease, the vital activity of the phytons or leaves diminishes, and the intervals between them gradually cease to form, until at length the elongation of the axis is wholly stopped. About this time the current of sap is diverted away from the leaves to the buds forming at the bottom of each leaf-stalk, and especially to the terminal bud which grows at the top of the shoot. This attraction of the sap or formative material away from the leaves by the newly-forming tissues of the buds, is undoubtedly one of the principal causes which produce their decay and separation from the shoot. When the leaves begin to change their color (the sure presage of their approaching fall), it is therefore an infallible indication that the sap is being diverted away from them to the buds, which have begun to grow, and that the shoot constructed by their united labors is about to be prepared for winter.

This preparation of the shoot for winter is effected by the development of another set of leaves, which other writers call bud-scales, but which I call (folia tegmentia) covering or protecting leaves. It is not nutrition, but protection which is required by the shoot during winter, and these leaves are organized expressly for this very purpose. They contribute nothing whatever to the support of the plant, but they shield it from the inclemency of the weather. It is

their duty to preserve from injury the amount of work already done. A beautiful vegetable cone has been constructed by the leaf-labor of the first year, and it is left in their charge.

In the beech-tree, the bud-scales or covering leaves acquire a somewhat horny texture. They are without pores, and are, in botanical language, imbricated; that is to say, they cover one another like the shingles on the roof of a house. Beneath these vegetable roofs, thus admirably constructed, the young branch charged with all the nutritive leaves of the next vegetative season lies imbedded in a warm downy investment.

Thus, even the defoliated shoot or vegetable cone is not without its attractions. There it stands, exposed to the fierce north wind, coated with ice from top to bottom. It matters not that the snow-covered ground, in which its roots lie imbedded, is frozen as hard as granite, for there are the protective leaves, or bud-scales. These are the appointed guardians of its life, and well do they perform their office. As soon as spring and warm weather come, do we not see the young shoots and the bright green leaves, which they have covered and protected, come forth uninjured? Exposure to the air, which is now mild and pleasant, will do the newly-developed shoots and leaves no harm, but is a positive benefit. The services of the covering or protective leaves of winter are therefore no longer required, and we see them fall, one by one from the stem. Why? Because they have fulfilled the purposes of Providence in their creation. They are, therefore, removed from the post of duty.

The Second Year's Growth.-With the gradual increase of light and heat the snow and ice disappears, the ground becomes soft and friable, the air mild and pleasant, and in the grand laboratory of organic nature all is again ceaseless activity. The same beautiful yet evanescent floral forms adorn the earth; the bright green grass, the leafy verdure of the woods charm the senses. Our vegetable cone with its lateral and terminal buds feels the effect of the genial influences that are abroad, and soon give signs of a renewed

vitality. The (folia tegmentia) covering-leaves separate from each other, and the new generation of nutritive leaves, sheltered by them through the winter months, are put forth uninjured into the atmosphere. The leaves proceeding from the bud at the summit of the vegetable cone, continue the growth of the main axis or stem, whilst those developed from the lateral buds give birth to branches. If now these new growths be carefully examined, it will be found that the new generation of leaves has constructed them on precisely the same plan as the first year's shoot. For these branches, and the addition which has been made to the stem in height, consist of precisely the same parts, viz.: a conical axis and leaves with buds in their axilla, and a terminal bud at the apex. Each new axis or shoot which has been superadded to the first year's shoot, must therefore be regarded as a simple repetition of the first year's shoot.

It is also plain that the branches are to the main axis or stem, the second year, what the leaves were to it the first year, performing precisely the same functions, only in a far more energetic manner; because in this case it is not one but several leaves which are engaged in elaborating the sap, which, when duly prepared in the leaves, passes from them into the main axis or stem of the tree through the common axis of the shoot, and thus contributes to its nutrition.

The tree has therefore a much greater amount of leaf-surface at work in the air the second year than it had the first, and its chances of life are consequently multiplied a thousand fold. For with every addition to the number of its leaves, the tree obtains a new instrument for extracting nutriment from the atmosphere, and elaborating such food as it attracts to itself from the soil. The amount of wood and bark formed is therefore much greater the second year than the first; it is, in fact, exactly proportionate to the increase in the extent of leaf-surface and the vital activity of the leaves themselves.

The sap having been exposed to the air and light in these additional leaf-surfaces, is again rendered nutritious, and