PART VI

THE POD-BEARING TREES

The Locusts--The Acacias or Wattles--Other Pod-bearers

Whenever we see blossoms of the sweet-pea type on a tree or pods of the same type as the pea's swinging from the twigs, we may be sure that we are looking at a member of the pod-bearing family, _leguminosae_, to which herbaceous and woody plants both belong. The family is one of the largest and most important in the plant kingdom, and its representatives are distributed to the uttermost parts of the earth. Four hundred and fifty genera contain the seven thousand species already described by botanists. Varieties without number belong to the cultivated members of the family, and new forms are being produced by horticulturists all the time. This great group of plants has fed the human race, directly and indirectly, since the First Man appeared on earth. Clovers, alfalfas, lentils, peas, beans yield foodstuffs rich in all the elements that build flesh and bone and nerve tissues. They take the place of meat in vegetarian dietaries.

Besides foods, the pod-bearers yield rubber, dyestuffs, balsams, oils, medicinal substances, and valuable timber. A long list of ornamental plants, beautiful in foliage and flowers, occurs among them, chiefly of shrub and tree form.

Last, but not least, among their merits stands the fact that leguminous plants are the only ones that actually enrich the soil they grow in, whereas the rest of the plant creation feed upon the soil, and so rob it of its plant food and leave it poorer than before.

Pod-bearers have the power to take the nitrogen out of the air, and store it in their roots and stems. The decay of these parts restores to the soil the particular plant food that is most commonly lacking and most costly to replace. Farmers know that after wheat and corn have robbed the soil of nitrogen, a crop of clover or cow peas, plowed under when green and luxuriant, is the best restorer of fertility. It enriches by adding valuable chemical elements, and also improves the texture of the soil, increasing its moisture-holding properties, which commercial fertilizers do not.

Seventeen genera of leguminous plants have tree representatives within the United States. These include about thirty species. Valuable timber trees are in this group. All but one, the yellow-wood, have compound leaves, of many leaflets, often fern-like in their delicacy of structure, and intricacy of pattern. With few exceptions the flowers are pretty and fragrant in showy clusters. The ripening pods of many species add a striking, decorative quality to the tree from midsummer on through the season. Thorns give distinction and usefulness to certain of these trees, making them available for ornamental hedges.

THE LOCUSTS

Three representatives of the genus _robinia_ are among our native forest trees. They are known in early summer by their showy, pea-like blossoms in full clusters, and their compound leaves, that have the habit of drooping and folding shut their paired leaflets when night comes on, or when rain begins to fall. The pods are thin and small, splitting early, but hanging late on the twigs.

=The Black Locust=

_Robinia Pseudacacia_, Linn.

The black or yellow locust is a beautiful tree in its youth, with smooth dark rind and slender trunk, holding up a loose roundish head of dark green foliage. Each leaf is eight to fourteen inches long, of nine to nineteen leaflets, silvery when they unfold, and always paler beneath. In late May, the tree-top bursts into bloom that is often so profuse as to whiten the whole mass of the dainty foliage. The nectar-laden, white flowers have the characteristic "butterfly" form, the banner, wings, and keel of the type pease-blossom. (_See illustration, page 198_). The bees lead the insect host that swarms about them as long as a locust flower remains to offer sweets to the probing tongues. Cross-fertilization is the advantage the tree gains for all it gives. The crop of seeds is sure.

The angled twigs of the black locust break easily in windy weather. The rapid growth of the limbs spreads the narrow head, and its symmetry is soon destroyed, unless the tree grows in a sheltered situation. An old locust is usually an ugly, broken specimen, ragged-looking for three-fourths of the year. The twigs look dead, because their winter buds are buried out of sight! The bark is dull, deeply cut into irregular, interlacing furrows, roughened by scales and shreds on the ridges. In winter the pods chatter querulously, as the wind plays among the tree tops.

The black locust is found from Pennsylvania to Iowa, and south from Georgia to Oklahoma. The lumber is coarse-grained, heavy, hard, and exceptionally durable in contact with the soil or water. This makes it especially adaptable for fence posts and boat bottoms. Crystals, called _raphides_, in the wood cells, take the edges off tools used in working locust lumber. Yet it is sought by manufacturers of mill cogs and wheel hubs, and railroad companies plant the trees for ties.

The locust-borer has ruined plantations of this tree of late years, and trees in the woods have become infested except in mountainous regions not yet reached by the pest. Trees become distorted with warty excrescences and the lumber is riddled with burrows made by the larvae. Until the entomologist finds a remedy in some natural parasite of the locust-borer, the outlook for locust culture seems dark enough. No insecticide can reach an enemy that hides in the trunk of the tree it destroys.

=The Clammy Locust=

_R. viscosa_, Vent.

The clammy locust has beautifully shaded pink flowers in clusters, each blossom accented by the dark red, shiny calyx, and the glandular exudation of wax, that covers all new growth. A favorite ornamental locust, this little tree has been widely distributed in this and other temperate countries of the globe. Its leaves are delicately feathery, with the dew-like gum brightening them, as it does also the hairy, curling pods that flush as they ripen. In winter the twigs are ruddy. The trees grow wild on the mountains of the Carolinas and nowhere else.

=The Honey Locust=

_Gleditsia triacanthos_, Linn.

The honey locust is a tall handsome flat-topped tree, with stiff horizontal, often drooping branches, ending in slim brown polished twigs, with three-branched thorns, stout and very sharp, set a little distance above the leaf scar of the previous season. Occasionally a thornless tree occurs.

Inconspicuous greenish flowers, regular, bell-shaped, appear in elongated clusters, the fertile and sterile clusters distinct, but on the same tree. The leaves are almost full-grown when the blossoms appear. Their feathery, fern-like aspect is the tree's greatest charm in early June. When the pods replace the flowers they attract attention and admiration as their velvety surfaces change from pale green to rose and they curve, as they lengthen, into all sorts of graceful and fantastic forms. The sweet, gummy pulp of the honey locust pods is considered edible by boys, who brave the thorns to get them. As the autumn approaches, the pulp turns bitter, and dries around the shiny black seeds. The purple pods cling and rattle in the wind long after the yellow leaves have fallen. One by one, they are torn off, their S-curves tempting every vagrant breeze to give them a lift. On the crusty surface of snowbanks and icy ponds, they are whirled along, and finally lodge, to rot and liberate the seeds. It takes much soaking to prepare the adamantine seeds for sprouting. The planter scalds his seed to hasten the process. Nature soaks, freezes, and thaws them, and thus the range of the honey locust is extended.

In the wild, this tree is found from Ontario to Nebraska, and south to Alabama and Texas. It chooses rich bottom lands, but is found also on dry gravelly slopes of the Alleghany Mountains. Trunks six feet in diameter are still in existence, preserved from the early forests of the Wabash Basin in Indiana. They tower nearly one hundred and fifty feet above the ground, and their branches are a formidable array of thorns (_see illustration, page 198_), that have grown into proportions unmatched in trees of slender build and fewer years. Such a veteran honey locust is one of the most picturesque figures in a winter landscape.

Honey locust wood is hard, coarse-grained, heavy, and durable in contact with water and soil. It is made into wheel-hubs, fence-posts, and fuel. In all temperate countries this species has been used as a shade and ornamental tree and as a hedge plant.

=The Kentucky Coffee Tree=

_Gymnocladus dioicus_, K. Koch

The Kentucky coffee tree is the one clumsy, coarse member of a family that abounds in graceful, dainty species. Its head is small and unsymmetrical, above a trunk that often rises free from limbs for fifty feet above ground. The branches are stiff and large, bare until late spring, when the buds expand and the shoots are thrown out. The leaves are twice compound, often a yard in length and half as wide; the leaflets, six to fourteen on each of the five to nine divisions of the main rib. No other locust can boast a leaf numbering more than one hundred leaflets, each averaging two inches in length. When the tree turns to gold in autumn, it is a sight to draw all eyes.

The flower spray is large, but the flowers are small, imperfect, salver-form, purplish green--the fertile ones forming thick, clumsy pods that dangle in clusters, and seem to weigh down the stiff branchlets. The fresh pulp used to be made into a decoction used in homeopathic practice. The ripe seeds were used in Revolutionary times as a substitute for coffee. How the pioneer ever crushed them is a puzzle to all who have tried to break one with a nut-cracker. In China the fresh pulp of the pods of a sister species is used as we use soap.

The wood is not hard, but in other respects it resembles other locust lumber. It is sometimes used in cabinet work, being a rich, reddish brown, with pale sap-wood.

The range of the coffee tree extends from New York to Nebraska, and south through Pennsylvania, Tennessee and Oklahoma, with bottom lands as the tree's preference. Nowhere is this species common. Occasionally, it is planted as a street tree, in this country and abroad.

=The Redbud=

_Cercis Canadensis_, Linn.

The redbud covers its delicate angled, thornless branchlets with a profusion of rosy-purple blossoms, typically pea-like, before the leaves appear. The unusual color, so abundant where little redbuds form thickets on the outskirts of a woodland, leads to a very general recognition of this tree among people who go into the April woods for early violets. It vies with the white banner of the shad-bush, in doing honor to the spring. Later, the broad heart-shaped leaves cover and adorn the tree, concealing the dainty tapering pods that turn to purple as the polished leaf blades, unmarred by insect or wind, change from green to clear yellow before falling.

Tradition has given this charming little locust tree the name, "Judas-tree," from its European cousin, rumored to have been the one upon which the choice of Judas fell when he went out and hanged himself. It is an unearned stigma, better forgotten, for it does prejudice the planter against a tree that should be on every lawn, preferably showing its rosy flowers against a bank of evergreens.

Its natural range extends from New Jersey to Florida and west from Ontario to Nebraska and southward. The largest specimens reach fifty feet in height in Texas and Arkansas, in river bottom lands, and in the Southwest the tree is an abundant undergrowth--making a beautiful woodland picture in early spring.

=The Yellow-wood=

_Cladrastis lutea_, K. Koch.

The yellow-wood was named by the wife of a pioneer, surely, for she soaked the chips and got from them a clear yellow dye, highly prized for the permanent color it gave to her homespun cotton and woolen cloth that must have gone colorless, but for dyestuffs discoverable in the woods.

The satiny grain of the wood, and its close hard texture, commended it to the woodsman, who used it for gun stocks. But the tree is too small to be important for the lumber it yields.

In winter the smooth pale bark of the "Virgilia," as the nurseryman calls it, reminds one of the rind of the beech. The broad rounded head, often borne on three or more spreading stems, is formed of drooping graceful branches, ending in brittle twigs. Summer clothes these twigs with a light airy covering of compound leaves, of seven to eleven broadly oval leaflets, on a stalk less than a foot in length. In autumn, the foliage turns yellow.

White flowers, pea-like, delicate, fragrant, in clusters a foot long, and so loose that the flowers seem to drip from the twig ends, drape the tree in white about the middle of June, when the young leaves show many tints of green to form a background for the blossoms.

This is the supreme moment of the year for one of the most charming of trees, in any park that cherishes one of these virgilias. In the wilds of eastern Tennessee, northern Alabama, and central Kentucky the species is found in scattered places. But the wild trees have scant food and they show it. The full beauty of the species is seen only in cultivation, as one sees it in the Arnold Arboretum, and in private gardens near Boston. Even the little pods, thin, satiny pointed, add a harmonious note of beauty; their silvery fawn color blending with the quiet Quaker drab worn by the tree all winter. Fortunately, this hardy beautiful park tree is easily raised from seeds and from root cuttings. It thrives on soil of many different kinds. It has no bad habits, no superior, and few equals among flowering trees.

THE ACACIAS, OR WATTLES

Australia has contributed to southern California's tree flora a large number of forms of the acacia tribe, shrubs and trees of great variety and beauty of flowers and evergreen foliage. They are hardy and perfectly at home, and are planted in such profusion as to be the commonest of all street and ornamental trees. The leaves are set on a branching pinnate stem, making them "twice compound" of many tiny leaflets, fascicled on the sides of the twigs, alternate on the terminal shoots of the season. The lacy, fern-like foliage of most acacias would justify the planting of them for this trait alone. But the abundant mass of bloom usually overwhelms the tree-tops, obscuring the foliage with a veil of golden mesh. Sometimes white, but oftenest yellow, the individual flowers are very small; but they crowd in button-like heads or elongated spikes, set close in axillary clusters. In their native woods these trees flower much less freely than in the land of their adoption. The curling pods are in most species and varieties ornamental, as they pass through many color changes before they finally discharge their seeds.

Acacias compose a genus of four hundred species, and an untold and constantly increasing number of cultivated varieties. The continent of Australia has the greatest representation of native species. Others belong to Africa--tropical, northern, and southern regions. Asia, in its warmer southern territory, and in southwestern China, has many native acacias. Tropical and temperate South America, the West Indies, Central America, Mexico, the southwestern region of the United States, and the islands of the South Pacific, all have representatives of this wonderful and far-scattered genus. There is no country interested in horticulture that does not grow acacias as ornamental shrubs and trees, even if they must be grown under glass the year round. In southern England the acacias, grown in open ground, and known as "tassel trees," attain good size.

Valuable lumber, tanbarks, dyes, perfumes, and drugs are yielded by acacias. Gum Arabic is the dried sap of several oriental species, particularly, _Acacia Arabica_, Linn. of Egypt and southern Asia.

As a rule, acacias have slender branches armed with spines. Often these are too small to attract notice, or to make the species useful as a hedge plant. All spines are modifications of the stipules at the base of leaf or leaflet. Thorns, however, are modified twigs, strong, stiff and sharp, often branched. The honey locust shows true thorns, not spines or prickles. The armament of canes of blackberry is only skin deep. This means of defence is best called "prickles."

=The Black Acacia=

_Acacia melanoxylon_

The black acacia, called at home in Australian woods, the "blackwood-tree," for its black heart-wood, is a familiar street and shade tree in California. In narrow parkings it is likely to surprise the planter by outgrowing in a few years the space allotted to it, and upheaving both cement walk and curb, by the irresistible force of its thick roots. It is one of the large timber acacias, and even in the cool climate of England reaches fifty feet.

In suitable situations in California it grows much higher, and its compact conical head of dense evergreen foliage, gives abundant shade at all seasons. The flowers are white or cream-colored, lightening the yellow-green of the new shoots and the dull, opaque of the older leaves, with abundant clusters in earliest spring. The succeeding fruits are curling thin pods that hang in brownish sheaves, giving the tree a rusty look. Each seed is rimmed with a frill of terra cotta hue that serves as a wing for its flight, when detached by the wind. The roots send up suckers and the seeds are quick to grow. So any one can have black acacias with little trouble or expense. Its shedding of leaves and pods makes much litter, however, a trait sometimes overlooked which seriously diminishes its desirability as a street and shade tree.

=The Silver Wattle=

_A. dealbata_

The silver wattle of nursery catalogues is named for its abundant, silvery-pubescent, feathery foliage. Its flowers--fluffy golden balls, small but abundant--make this a wonderfully showy tree.

Sea-green and turquoise-blue leaves, with abundant canary-yellow bloom, are traits of many different acacias in cultivation, all of which are rapid growers, and soon repay the planter who wants quick results. From being mere ornaments they rise to the stature of shade trees, and merely multiply the charms that made them admired when young. Varieties with sharp spines are employed as hedge plants. Curious leaf forms and unusual, edgewise position of the foliage, make us wonder at some of the glorious "golden wattles" and "knife-leaved acacias," that bring us glimpses of the forests of Australia and other strange far countries.

OTHER POD-BEARERS

=The Mesquite=

_Prosopis juliflora_, DC.

The mesquite or honey pod is one of the wonderful plants of the arid and semi-arid regions from Colorado and Utah to Texas and southern California. At best it is a tree sixty feet high along the rivers of Arizona. In the higher and more desert stretches it is stunted to a sprawling shrub, with numerous stems but a few feet high. Its leaves are like those of our honey locust but very much smaller, and the tree furnishes little shade. The bark of the trunk is thick, dark reddish brown, shallowly fissured between scaly ridges. In winter the tree looks dead enough, but the young shoots clothed with tender green bring it to life in early spring, and the greenish fragrant flowers, thickly set in finger-like clusters, appear in successive crops from May to July. These are succeeded by pods four to nine inches long in drooping clusters, each containing ten to twenty beans.

Not its beauty of leaf and blossom but its usefulness is what makes this tree almost an object of worship to desert dwellers, red men and white. The long fat pods supply Mexicans and Indians with a nutritious food, green or ripe. Cattle feed upon the young shoots and thrive, when other forage is scant or utterly lacking. The fuel problem of the desert is solved by the mesquite in a way that is a great surprise to the newcomer. His sophisticated neighbor takes him on a wood-gathering expedition. Stopping where a shrubby mesquite sprawls, he hitches his team to a chain or rope that lays hold of the trunk, and hauls the plant out by its roots. And what roots the mesquite has developed in its search for water! There is a central tap root that goes down, down, sometimes sixty feet or more. Secondary roots branch out in all directions, interlock, thicken, and form a labyrinth of woody substance, in quantity and quality that makes the timber above ground a negligible quantity. This wood is cut into building and fencing materials--two great needs in the desert. The waste makes good fuel, and every scrap is precious. Posts, railroad ties, frames for the adobe houses, furniture, fellies of wheels, paving blocks, and charcoal are made of this wonderful tree's root system. A gum resembling gum-arabic exudes from the stems.

=The Screw-bean=

_P. pubescens_, Benth.

The screw-bean or screw-pod mesquite is a small slender-trunked tree with sharp spines at the bases of the hoary foliage. The marked distinction between this species and the preceding one is in the fruit, which makes from twelve to twenty turns as it matures, and forms when ripe a narrow straight spiral, one to two inches long; but when drawn out like a coiled spring the pod is shown to be more than a foot in length. These sweet nutritious pods are a most useful fodder for range cattle, and the wood is used for fencing and fuel. This tree grows from southern Utah and Nevada through New Mexico and Arizona into San Diego County, California, western Texas and northern Mexico.

=The Palo Verde Acacia=

_Cercidium Torreyanum_, Sarg.

The palo verde is another green-barked acacia whose leaves are almost obsolete. Miniature honey-locust leaves an inch long unfold, a few here and there in March and April, but they are gone before they fully mature, and the leaf function is carried on entirely by the vivid green branches. Clustered flowers, like little yellow roses, cover the branches in April, and the pointed pods ripen and fall in July.

In the Colorado desert of southern California, in the valley of the lower Gila River in Arizona, on the sides of low canyons and on desert sandhills into Mexico, this small tree, with its multitude of leafless, ascending branches, is one of the brightest features on a hopelessly dun-colored landscape.

=The Jamaica Dogwood=

_Icthyomethia Piscipula_, A. S. Hitch.

The Jamaica dogwood is a West Indian tree that grows also in southern Florida and Mexico. It is one of the commonest tropical trees on the Florida West Coast from the shores of Bay Biscayne to the Southern Keys. The leaves are four to nine inches long, with leaflets three to four inches in length, deciduous, vivid green, making a tree fifty feet high an object of tropical luxuriance. Its beauty is greatly enhanced in May by the opening of the pink, pea-like blossoms that hang in drooping clusters a foot or more in length. The necklace-like pods are frilled on four sides with thin papery wings.

The wood of this tree is very durable in contact with water, besides being heavy, close-grained, and hard. It is locally used in boat-building, and for fuel and charcoal. All parts of the tree, but especially the bark of the roots, contain an acid drug of sleep-inducing properties. In the West Indies the powdered leaves, young branches, and the bark of the roots have long been used by the natives to stupefy fish they try to capture.

=The Horse Bean=

_Parkinsonia aculeata_, Linn.

The horse bean or retama, native to the valleys of the lower Rio Grande and Colorado River, is a small graceful pod-bearing tree of drooping branches set with strong spines, long leaf-stems, branching and set with many pairs of tiny leaflets.

The bright yellow, fragrant flowers are almost perennial. In Texas the tree is out of bloom only in midwinter. In the tropics, it is ever-blooming. The fruit hangs in graceful racemes, dark orange-brown in color, and compressed between the remote beans. As a hedge and ornamental garden plant, this tree has no equal in the Southwest. It is met with in cultivation in most warm countries.

=The Texas Ebony=

_Zigia flexicaulis_, Sudw.

The Texas ebony is a beautiful, acacia-like tree of southern Texas and Mexico. One of the commonest and most beautiful trees on the bluffs along the coast, south of the Rio Grande. Its leaves are feathery, fern-like, its flowers in creamy clusters, its pods thick, almost as large as those of the honey locust. The seeds are palatable and nutritious, green or ripe. Immature, the pods are cooked like string beans; ripe, they are roasted, and the pods themselves are ground and used as a substitute for coffee.

The wood is valuable in fine cabinet work, and because it is almost indestructible in contact with the ground, it is largely used for fence posts. It makes superior fuel. Besides being more valuable than any other tree of the Rio Grande Valley, though it rarely exceeds thirty feet in height, it is worthy of the attention of gardeners as well as foresters in all warm temperate countries. Prof. Sargent calls it the finest ornamental tree native to Texas.

=The Frijolito=

_Sophora secundiflora_, DC.

The frijolito or coral-bean is a small, slender narrow-headed tree, with persistent, locust-like leaves, fragrant violet-blue flowers, and small one-sided racemes. The pods are silky white, pencil-like, constricted between the bright scarlet seeds. The tree grows wild in canyons in southern Texas and New Mexico, forming thickets or small groves in low moist limestone soil and stream borders. It is a close relative of the famous pagoda tree of Japan, _S. Japonica_, universally cultivated; and it deserves to be a garden tree throughout the Southern states.