American Forest Trees Part 56

WHITE POPLAR (_Populus alba_) is a European species but has become naturalized in the United States. It is widely planted as a shade tree, and has escaped from cultivation. It may be known by the white undersides of its small leaves, and by its yellowish-green bark which remains smooth, except on large trunks. It is not yet important as a source of lumber, but the vigor of its growth indicates that it may sometime become so. The wood is soft, white, and light. Some persons consider the tree objectionable as an ornament because of its habit of sending up sprouts from the roots, and because its woolly leaves collect dust and smoke until they are almost black by the end of summer.

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MANGROVE

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MANGROVE

(_Rhizophora Mangle_)

The mangrove family is large and widely scattered, but only one member has gained a foothold in the United States, and it occupies only limited areas in south Florida, at the delta of the Mississippi, and on the coast of Texas. The family's fifteen genera are confined to the tropics, with a little overlapping on the temperate zones. The botanical name _Rhizophora_ refers to the tree's peculiar roots, and _mangle_ is the Spanish for mangrove. This is one of the few trees in this country which are known by a single name. It is always called mangrove, and attains its best development in Florida.

The leaves hang two years, are from three to five inches long and one or two wide. Flowers are not showy, but they are nearly always present, blooming the year round, the yellow blossom about an inch in diameter.

The fruit proper is about an inch long, but its habit of sprouting while still on the tree and sending down a long stem-like root, gives the impression that the fruit is several inches long, sometimes a foot.

It is not an easy matter to state the average size of mangrove trees.

Peculiar habits of growth make measurements difficult. Neither is it easy to tell where a tree begins and where it ends. Mangrove thickets along some of the rivers of south Florida, within the influence of tide water, are strange forms of vegetation. If the foliage alone is considered from a little distance, it reminds one of a row of fig trees in Louisiana or California. The color and general appearance suggests fig trees. A nearer approach reveals beneath the crowns a ma.s.s of roots, stems, and limbs, joined with the ground beneath and the crowns above.

In addition to these, there are many others that dangle from above, like rope ends, some nearly touching the ground, others several feet above.

These are roots or limbs, by whichever name one cares to call them. They grow from overhead branches, and strike for the ground. When they touch the soil, they quickly anchor themselves, and become stems. They then look like slender poles set as props under the branches of an overladen fruit tree.

This strange habit of growth gives the tree its character. Most mangroves stand in water. They fringe the banks of rivers and bayous, extending the fringe as far as the water is shallow. Growth of that kind is generally from ten to twenty feet high, and the largest stems from an inch in diameter up to three or four; but these dimensions cannot be taken as limits to size. Sometimes the trees are sixty or seventy feet high, but those which stand in water seldom reach that size. Trees which have their beginning in the water sometimes end their days high and dry on the land.

The mangrove is a land builder. The sycamore and willow are land builders on a small scale, along northern water-courses, but mangrove excels them a hundred or a thousand fold where it grows on the low sh.o.r.es of Florida. The seed is prepared for land-building work before it drops from the tree. It sprouts a long, peculiar root--it looks like a very slender, big-ended cuc.u.mber--the large, heavy end down. This attains a length of several inches or a foot. When it drops from the branch, the end sticks in the mud and takes root, grows, and produces a tree. But generally it falls in water, and not on a mud bank. In that case it floats away, the heavy end down, the light end barely appearing on the surface. Winds and currents drive it about until the lower tip finally touches bottom in some shallow place. There it takes root, and unless circ.u.mstances are extremely adverse, it holds fast, finally becomes a tree, sends branches down from above to take root at the bottom of the water, and a clump is produced. The tangled ma.s.s of stems and roots catches driftwood and mud, resulting finally in a little island, and later the island is joined to the mainland. Thus the land is built. Many large flats in Florida owe their origin to this tree. When land is permanently above water, the mangrove loses, to some extent, its ability to send roots down from the limbs. Nature seldom does something for nothing, and since the mangrove's aerial roots no longer serve a useful purpose in nature's economy, they are dispensed with. Trunks then reach much larger size, and become timber instead of thickets. The accompanying picture shows a mangrove that no longer stands in water, and its habit of growth is changing.

Thickets of mangrove are useful, not only in building new land, but in protecting that already built. Frequently the force of waves is broken, which otherwise would destroy low sh.o.r.es. Tremendous seas, in time of storms, will roll over thickets of mangrove without uprooting them or breaking the stems. Again nature's fine engineering is apparent. When men build lighthouses which must endure the shocks of waves, they have learned to construct them of open beams and lattice work. The wave pa.s.ses through without delivering the full impact of the blow to the structure. No solid masonry will stand what a comparatively light open frame will endure without injury, because it allows the waves to pa.s.s on. A large wave may strike with a force of 6,000 pounds to the square foot. The mangrove thickets are like the open-framed lighthouse--they let the waves pa.s.s through and spend their force gradually beyond, but they hold the sh.o.r.e against washing.

Admirable and wonderful as is nature's provision for protecting the land by a fringe of lattice work of branches and stems, the marvelous efficiency of the provision has been greatly increased in another way.

Suppose, for ill.u.s.tration, that cottonwood instead of mangrove formed the protective thickets along stormy sh.o.r.es. The first hour of heavy seas would reduce the trees to fragments. The weak, brittle trunks and limbs would quickly break to pieces. But mangrove pa.s.ses through storm after storm unharmed. It is scarcely believable that accident accounts for the fact that the best wood for the place is in the place; but it is probable, rather, that ages of development and natural selection gave to mangrove the qualities which make possible the accomplishment of its work. It is one of the strongest, and as far as available data may be depended upon, it is absolutely the most elastic wood in the United States. Sh.e.l.lbark hickory is rated high in both strength and elasticity; but mangrove rates higher. Sargent gives hickory's measure of elasticity at 1,925,000 pounds per square inch; but mangrove's is 2,333,000 pounds.

It is thus fitted in the highest manner to perform the work needed. It plants itself in the right place; develops stems which will endure most and suffer least; possesses enormous strength for resisting force, yet is so extremely elastic that the force of waves is exhausted upon the trunks and branches without flattening them upon the ground or crushing them. Few things of the vegetable world show more perfect adaptation to environment. The wood's very heaviness seems to add one more quality fitting it for its place. When a trunk falls in the water, it does not float away as most trees would, but sinks like iron, lies on the bottom, helps to hold the forming island or bar in place, and in its death as in its life it is a land-builder. Its efficiency in that particular is increased by the fact that it is little affected by marine borers which, in the warm, brackish waters, usually destroy wood in a short time.

Mangrove is not important commercially, though it is used for a number of purposes. The wood weighs 72.4 pounds per cubic foot, takes good polish, though it is inclined to check in drying; it contains many small pores; medullary rays numerous and thin; color reddish-brown streaked with lighter brown. The princ.i.p.al use of the bark is for tanning and the trunks for piles. It is well fitted for fence posts, but not many have been used in the region where it grows. It rates high as fuel, but its great weight increases transportation charges if the haul is long.

Tanbark peelers in Florida have cut much of the large mangrove forest.

They took the bark, and abandoned the trunks. There is no likelihood that the species will be exterminated. Much of the growth is practically inaccessible, and the trunks are too small to tempt bark peelers, and cordwood cutters find plenty of material more convenient.

OTHER SPECIES.--Two other trees of this country are called mangrove though they are not even in the same family. One is the black mangrove (_Avicennia nitida_), called also blackwood and black tree.

It is a Florida species of the family Verbenaceae, and has some of the mangrove's habits. It takes root and grows on muddy sh.o.r.es and is a land builder. The largest trees are sixty or seventy feet high and two in diameter, but are usually less than thirty feet high. The bark is used in tanning, and no use for the wood is reported, except for fuel. White mangrove (_Laguncularia racemosa_), known also as white b.u.t.tonwood, is a Florida species. It attains a height of thirty or forty feet and a diameter of a foot or more. It reaches its largest size on the sh.o.r.es of Shark river, Florida. The wood is dark yellow-brown, and the bark is rich in tannin, and the tree may become valuable as a source of tanbark.

Near akin to white mangrove is Florida b.u.t.tonwood (_Conocarpus erecta_) which is highly esteemed as fuel. It burns slowly like charcoal. Trees are from twenty to fifty feet high. Its range lies in southern Florida. Black olive tree (_Terminalia buceras_) belongs in the south Florida group, and the wood is exceedingly hard and heavy. The trunk is often two or three feet in diameter, but lies on the ground like a log, with upright stems growing from it. Tanners make use of the bark.

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CABBAGE PALMETTO

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THE PALMS

Lumbermen in this country could get along very well without the palms, as they are little used for ordinary lumber. Their wood does not grow in concentric rings, like that of the ordinary tree. The stems are usually single, cylindrical, and unbranched. The fruit is berry-like, and is usually one seeded, though sometimes there are two or three. When a seed sprouts, it puts out at first a single leaf, like a grain of corn. About 130 genera of palms are recognized in the world, most of them in the tropics, but several in the United States are of tree size. Botanists divide the palms of the United States into two groups, the palm family and the lily family. The yuccas belong in the lily family. In the very brief treatment that can be given the subject here, it is not necessary to recognize strict family divisions.

CABBAGE PALMETTO (_Sabal palmetto_) grows in the coast region from North Carolina to southern Florida, and west to the Apalachicola river. It is sometimes called Bank's palmetto, cabbage tree, and tree palmetto. The name cabbage is due to the large leaf-bud in the top of the stem which is cooked as a subst.i.tute for cabbage. A sharp hatchet and some experience are necessary to a successful operation in extracting the bud from the tough fibers which surround it.

This palm is a familiar sight in the coast region within its range. The tall trunks, with tufts of leaves at the tops, suggest the supposed scenery of the Carboniferous age. Usually the trunks, in thick stands, rise straight like columns from twenty to forty feet high, but occasionally they bend in long, graceful curves, as if the weight of the tops caused them to careen, which is probably what does happen. They vary in diameter from eight inches to two feet.

The leaves are five or six feet long, and seven or eight wide, with stems six or seven feet long. Flowers occur in racemes two feet or more in length. The fruit is spherical and about a third of an inch in diameter. The roots are an important part of this palm, and are adapted to their environment, forming a rounded ma.s.s four or five feet in diameter, while small rope-like roots, half an inch in diameter, penetrate the wet marshy soil fifteen or twenty feet. The large, globe-like ma.s.s gives support in the soft soil, and the stringy roots supply water and mineral substances essential to growth. The wood is light, soft, pale-brown, with numerous hard, fibro-vascular bundles, the outer rim about two inches thick and much lighter and softer than the interior. The most important use for the wood at present is as wharf piles. It lasts well and is ideal in form. It is of historical interest that Fort Moultrie which defended Charleston, South Carolina, in the Revolutionary war, was built of palmetto logs. When the British made their memorable attack in 1776, their cannon b.a.l.l.s buried in the spongy logs without dislodging them, and the fort successfully withstood the bombardment of ten hours, and disabled nine of the ten British ships taking part in the a.s.sault.

The wood is employed to a small extent in furniture making, and the bark for scrubbing brushes. Some of the finest forests of palmetto in Florida are much injured by fire that runs up the trunks to feed on stubs of leaves.

SILKTOP PALMETTO (_Thrinax parviflora_) and silvertop palmetto (_Thrinax microcarpa_) are species met with on some of the islands off the coast of southern Florida.

MEXICAN PALMETTO (_Sabal mexicana_) is much like cabbage palmetto in size and general appearance, and is put to similar uses, except that the leaf-bud does not appear to be used as food. The tree occurs in Texas along the lower Rio Grande, and southward into Mexico where the leaves are employed as house thatch by improvident Mexicans and Indians who do not care to exert themselves to procure better roofing material. In the vicinity of Brownsville, Texas, trunks of this palm are employed as porch posts and present a rustic appearance. They are said to last many years. The average size of trunks in Texas is fifteen or twenty feet high and a foot or less in diameter, but some much larger are found in Mexico. Some of the wharfs along the Texas coast are built on palmetto piles. It is said the trunks are not as strong as those of the cabbage palmetto in Florida.

SARGENT PALM (_Pseudophnix sargentii_) is interesting but not commercially important, but may become so as an ornamental plant. It is occasionally planted on lawns in south Florida. Leaves are five or six feet long with stems still longer. The cl.u.s.ters of flowers are sometimes three feet in length. A single species is known, occurring on certain keys in southern Florida, and is so limited in its range that it would be possible to count every tree in existence. A grove of 200 or 300 trees occurs on Key Largo.

ROYAL PALM (_Oreodoxa regia_) is one of the largest palms of this country. It is said to reach a height of eighty feet, but such sizes are rare. The trunk rises from an enlarged base, and may be two feet in diameter. Bark is light gray in color, and its appearance suggests a column of cement. Leaves are ten or twelve feet long, and the stems increase the total length to twenty feet or more. Flowers are two feet in length, and in Florida open in January and February. The fruit is smaller than would be expected of a tree so large. It is a drupe about the size of a half-grown grape. The wood is spongy, but the outer portion of the stem is strong and is made into canes and other small articles. Trunks are sometimes used as wharf piles. This palm's range is confined to south Florida in this country, but it is common in the West Indies. In Miami and other towns of southern Florida it is much planted for ornament.

FANLEAF PALM (_Neowashingtonia filamentosa_) also called Washington palm, California fan palm, Arizona palm, and wild date, ranges through southern California, and occupies depressions in the desert west of the Colorado river. There are said to be several forms and varieties. It ranges in height from thirty-five to seventy feet and in diameter from twenty to thirty inches. Trunks are of nearly the same diameter from bottom to top, or taper very gradually. They usually lean a little. Dead leaves hang about the trunks and blaze quickly when fire touches them, but the palm is seldom killed by fire. The small black fruit is about a third of an inch in diameter, and of no commercial importance; wood is little used; and the tree is chiefly ornamental, and has been much planted in California.

MOHAVE YUCCA (_Yucca mohavensis_) is one of a half dozen or more palms of the yucca genus and the lily family. Trees of this group are characterized by their stiff, sharp-pointed leaves, some of which are called daggers and others bayonets. Both names are appropriate. The Mohave yucca takes its name from the Mohave desert in California, where it is occasionally an important feature of the doleful landscape. The ragged, leather-like leaves, forming the tops of the short, weird trees, rattle in the wind, or resound with the patter of pebbles when sandstorms sweep across the dry wastes. It is believed to be one of the most slowly-growing trees of this country. Trunks are seldom more than fifteen feet high and eight or ten inches in diameter. The wood is spongy and interlaced with tough, stringy fibers. Stockmen whose ranges include this tree, make corrals of the stems by setting them in the ground as palisades. When weathered by wind and made bone dry by the sun's fierce heat, the trunks are reduced to almost cork-lightness.

Other yuccas are the Spanish bayonet (_Yucca treculeana_) of Texas; Joshua-tree (_Yucca arborescens_), which ranges from Utah to California and is known as tree yucca, yucca cactus, and the Joshua; Schott yucca (_Yucca brevifolia_) of southern Arizona; broadfruit yucca (_Yucca macrocarpa_) of southwestern Texas; aloe-leaf yucca (_Yucca aloifolia_) with a range from North Carolina near the coast to Louisiana; and Spanish dagger (_Yucca gloriosa_), on the coast and islands of South Carolina.

GIANT CACTUS (_Cereus giganteus_) is a leafless tree of Arizona and attains a height of forty or sixty feet, diameter of one or two.

About twenty genera of cactus are known in the world and a large number of species. Two genera, the cereuses and opuntias, have representatives of tree size in this country. The two genera differ in form. Cereus in the Latin language means a candle, and the cactuses of that genus stand up in straight stems like candles, or have branches like old-fashioned candlesticks. The opuntias have flat, jointed stems, like thick leaves. Giant cactus bears flowers four inches long and two wide; fruit two inches long and one wide, and edible. Indians derive a considerable part of their food from this cactus. They use the wood for rafters, fences, fuel, lances, and bows. The trunks consist of bundles of fiber, very hard and strong. In the dry region where this cactus grows, the woody parts of fallen stems last long periods, some say for centuries, but there are no records. Schott cactus (_Cereus schottii_) and Thurber cactus (_Cereus thurberi_) are found in southern Arizona and southward in Mexico.

CHOLLA (_Opuntia fulgida_) ranges from Nevada southward into Mexico.

It is popularly called "divil's tongue cactus," but there are other species with the same name. Trunks are occasionally ten or twelve feet high, and the wood is made into canes and small articles of furniture, but as lumber it is not important. The fruit is not eaten. A closely-related species is known as ta.s.sajo (_Opuntia sponsior_). It is found on the dry mesas of southern Arizona where trunks may be ten feet high and a few inches in diameter. It has the same uses as cholla. A third species is _Opuntia versicolor_ of southern Arizona. It is similar to the other opuntias. Attempts have been made to grow spineless varieties of this group of cactuses. It is believed that cattle, sheep, and goats would thrive on the pulpy growth, if the thorns could be gotten rid of. The semi-desert regions of the Southwest produce enormous quant.i.ties of cactus of many kinds, and if those worthless species could be made way with and thornless varieties subst.i.tuted, it is probable that much land now worthless would become valuable.

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