CHAPTER XVII.—BOTANY.
The vegetation of the United States is as various as the climate and soil. In Florida and the southern states, the superb magnolia, the majestic tulip tree and the deciduous cypress charm the traveller by their grandeur and beauty. The lofty oak, the stately fir and the gracefully-waving elm of the north, present a different and still a highly interesting study to the naturalist. As a general observation, the trees of the United States are larger, taller, and more generally useful for timber than those of Europe. As to height, it is observed by Michaux, that, while in France only thirty-seven species of trees arrive at thirty feet, in the transatlantic republic, one hundred and thirty exceed that elevation. A general idea of the American forest having thus been given, we will now notice, as largely as our limits will permit, the most remarkable trees.
Oak.—The White Oak is found throughout the United States, though it is by no means equally diffused. It abounds chiefly in the middle states, particularly in that part of Pennsylvania and Virginia which lies between the Alleghanies and the Ohio, a distance of about one hundred and fifty miles, where nine tenths of the forests are frequently composed of these trees, whose healthful appearance evinces the favorable nature of the soil. East of the mountains, this tree is found in every exposure, and in every soil which is not extremely dry or subject to long inundations; but the largest stocks grow in humid places. In the western districts, where it composes entire forests, the face of the country is undulated, and the yellow soil, consisting partly of clay with calcareous stones, yields abundant crops of wheat.
The white oak attains the elevation of seventy or eighty feet, with a diameter of six or seven feet; but its proportions vary with the soil and climate. Soon after their unfolding, the leaves are reddish above and white and downy beneath; when fully grown, they are smooth and of a light green on the upper surface. In autumn, they change to a bright violet color, and form an agreeable contrast with the surrounding foliage which has not yet suffered by the frost. This is the only oak on which a few of the dried leaves remain till the circulation is renewed in the spring. By this peculiarity and by the whiteness of the bark, from which it derives its name, it is easily distinguishable in the winter. This tree puts forth flowers in May, which are succeeded by acorns of an oval form, large, very sweet, contained in rough, shallow, grayish cups, and borne singly or in pairs, by peduncles eight or ten lines in length, attached, as in all species of annual fructification, to the shoots of the season. The fruit of the white oak is rarely abundant, and frequently, for several years in succession, a few handfuls of acorns could hardly be collected in a large forest where the tree is multiplied. Some stocks produce acorns of a deep blue color.
Of all the American oaks, this is the best and the most generally used, being strong, durable, and of large dimensions. It is less employed than formerly in building, only because it is scarcer and more costly. Amongthe uses of this wood, the most important is in ship-building. In all the dock yards of the northern and middle states, except Maine, it is almost exclusively employed for the keel, and always for the lower part of the frame and the sides: it is preferred for the knees, when sticks of a proper form can be found. In the smaller ports south of New York, the upper part of the frame is also made of white oak; but such vessels are less esteemed than those constructed of more durable wood. The medicinal properties of oak bark depend on its astringency, and that again on its tannin. The inner bark of the small branches is the strongest, the middle bark next, and the outer bark is almost useless.
The Gray Oak, Water Oak, Bear Oak, Upland, Willow Oak, and Bartram Oak are interesting varieties. The Laurel Oak is a stranger north of Philadelphia, and is rare in the more southern states. It is most abundant in the open savannas of Illinois. Rising to the height of forty or fifty feet, clad in a smooth bark, and for three fourths of its height laden with branches, it presents an uncouth appearance when bared by the winter blasts, but in the summer with its thick tufted foliage is really beautiful. The Black Oak is found throughout the country, with the exception of the northern part of New England. It is one of the loftiest of the American forest trees, rising to the height of eighty or ninety feet, with a diameter of four or five feet. The wood is reddish and coarse-grained, with empty pores, but is esteemed for strength and durability. It furnishes excellent fuel, and the bark is largely used for tanning. Other varieties of the oak are numerous.
Walnut.—The Black Walnut is met with in large numbers in the forests in the vicinity of Philadelphia, and with the exception of the lower parts of the southern states, where the soil is too sandy, or too wet as in the swamps, it is met with to the banks of the Mississippi throughout an extent of two thousand miles. East of the Alleghanies in Virginia, and in the upper parts of the Carolinas and Georgia, it is chiefly confined to the valleys where the soil is deep and fertile, and which are watered by creeks and rivers. On the banks of the Ohio and on the islands of this beautiful river, the black walnut attains the elevation of sixty or seventy feet, with a diameter of three to seven feet. Its powerful vegetation clearly points out this, as one of the largest trees of America. When it stands insulated, its branches, extending themselves horizontally to a great distance, spread into a spacious head, which gives it a very majestic appearance. The bark is thick, blackish, and on old trees deeply furrowed. The leaves when bruised emit a strong aromatic odor.
When the wood of this tree is freshly cut, the sap is white and the heart of a violet color, which, after a short exposure to the air, assumes an intenser shade, and becomes nearly black: hence probably is derived the name Black Walnut. There are several qualities for which its wood is principally esteemed: it remains sound for a long time, even when exposed to the influences of heat and moisture; but this observation is only applicable to the heart, the sap speedily decays: it is very strong and very tenacious: when thoroughly seasoned, it is not liable to warp and split; and its grain is sufficiently fine and compact to admit of a beautiful polish. It possesses, in addition to these advantages, that of being secure from worms. On account of these excellencies, it is preferred and successfully employed in many kinds of work. East of the Alleghanies, its timber is not extensivelyused in building houses, but, in some parts of Kentucky and Ohio, it is split into shingles which serve to cover them: sometimes also this timber enters into the composition of the frame. But it is chiefly in cabinet-making, that this wood is employed wherever it abounds.
There are several other species of the walnut. The Shell-bark Hickory sometimes grows to the height of eighty or ninety feet, with a diameter of less than two feet; the trunk is destitute of branches, regularly shaped, and almost of a uniform size for three fourths of its length. The Butternut is found in all the New England states, and in the middle states.
Maple.—The Sugar Maple, called also rock maple, has leaves five-parted, and yellowish green flowers, and is one of the loftiest trees in our forests. Its trunk is usually straight and entire, to the height of from forty to eighty feet, where it suddenly unfolds into a dense top, crowded with rich foliage. The bark of the older trees is gray, and marked with numerous deep clefts. The wood is firm and heavy, though not durable. It is much used by cabinet-makers, and when cut at the right season forms excellent fuel. Michaux says, that it grows in its greatest perfection, between the forty-third and forty-sixth degrees of north latitude.