Endogenous plants have no real bark on their stems; the external coats of wood are so much hardened as to render such a preservation unnecessary. Some of our most useful and ornamental plants belong to this divisioncorn, sugar cane, all the cereals, all the grasses, and all the lilies and bulbousrooted plants.

To the exogens belong all the useful and fruit-bearing trees and shrubs of temperate climes; to them the remainder of this report will be devoted. If we cut across a young twig of any common tree or shrub, such as the ash, maple or elm, we shall observe that it consists of three distinct parts, ordinarily known as pith, wood, and bark. The pith is a soft, spongy substance, occupying the center; if a thin slice of it be cut, either across or vertically, and magnified, it is seen to consist of cellular tissue, the cells of which are mostly of a very regular form. This soft, pulpy body does not grow or increase in size with the tree, but retains the same dimensions it had originally in the young stem. When young it contains a good deal of fluid, and has a greenish hue; when the stem is older, it becomes white and dry, and in very old trees it is often found to have shriveled up and almost entirely disappeared. The first layer surrounding the central pith grows freely during the first season, but the following year it is inclosed by a new layer; being by the pressure of this layer prevented from extending laterally, it makes its way where there is no pressure, that is to say, vertically. When, during the third season, a third layer surrounds and compresses the second, this, in its turn, escapes from the bondage by rising vertically. This process goes on year after year, so that the stem grows in height at the same time that it increases in thickness. This mode of growing renders the form of the stem conical, the number of layers diminishing as the stem rises. During this annual growth the prolongations of the pith still exist, but they become narrower in each ring and at last appear merely as lines diverging from the center. These are termed medullary rays, and their office is to maintain a constant connection between the pith and interior of the stem and the bark or exterior. The thin plates which they form, crossing as they do the direction of the fibers of the wood, are known to cabinet-makers as the silver grain.

These layers of wood attain a state of maturity when they become so hard, by continued pressure, as to be no longer susceptible of yielding to it. The number of rings denote the number of years the stem has existed. But there is reason to believe that in tropical climes, where many species of trees have two and even three successions of leaves in a year, a corresponding number of layers will be formed.

The wood is inclosed by the bark, which is, like it, formed in regular layers, only the growth is precisely the inverse of that of the wood; that is to say, it is endogenous, its layers growing internally. The new soft coat of bark, therefore, lies immediately in contact with the new soft layer of wood. Near the close of the spring the bark becomes loosened from the wood, with which it was previously in close contact, and a glutinous fluid, termed the

cambium, is found between them. This may be observed by stripping the bark from almost any twig at that season of the year. The outer coats of bark frequently do not grow so rapidly as the woody layers beneath, and the stem becomes hide-bound. We have a familiar example in the Morello cherry. In the case of the birch, the epidermis alone fails to grow, and it is thrown off in ribands. In the plane tree, (Platanus occidentalis,) the whole cortical envelope is hurt and falls away. It is this which produces the ruggedness in the stem of the apple tree. In the grape-vine the whole bark is thrown off annually. This is also seen in the oak, (Quercus suber,) in which the cellular layer is so largely developed that it is used extensively in the arts by the name of cork. It is in the vessels and woody tubes of the alburnum (or white wood) that the fluid absorbed by the roots is transmitted to the opposite extremity of the stem; and these vessels communicate with those of the leaves, which receive it from them. In the liber (or inner layer of the bark) the woody tissues have a somewhat different form, and it has been supposed by some, because they differ, that they are destined to a different function from that performed by the woody fibers of the alburnum. The function attributed to them is that of conveying back from the leaves the juices of the plants which have been there elaborated out of the sap brought up by the vessels of the alburnum. This has been called by many theoretical writers "the descent of the sap." There is, however, good reason to doubt as to whether there is any such definite descent of the sap as is taken for granted by the above theory. Our settled conviction is, after fifty years' observation and close attention, that the sap does not descend at all, but is elaborated and retained during its upward flow. But we are anticipating a future report on the "Circulation of the Sap."

As the bark is sufficiently distensible to admit of the increased diameter of the interior of the stem, there is no necessary limit to the age of exogens, and there are many unquestionable examples of such trees having obtained an enormous longevity. At Ellerstic, in Scotland, the birth-place of the immortal Wallace, exists an oak, which is celebrated as having been a remarkable object in his time; and which can scarcely, therefore, be less than 700 years old. Near Staines, England, there is a yew tree older than Magna Charta, and the seven yew trees at Fountains Abbey, in Yorkshire, are probably more than 1200 years old. Fruit-bearing trees seldom attain a great age. Downing refers to two apple trees in 1848, which were then 140 years old. We recollect seeing in 1830 the original Hawthornden apple tree, at that time over two hundred years old. There are pear trees on record in Europe of great size and age. M. Bosc mentions several which are known to be over 400 years old. There is a very extraordinary tree in Home Lacy, Herefordshire, England-a perry pear-from which were made more than once, 15 hogsheads of perry in a single year. In 1805 it covered more than half an acre of land, the branches bending down and taking root, producing others. Loudon, in his work on trees, says it is still in fine health.

Another specimen, perhaps the oldest in this country, is the Stuyvesant pear tree, originally planted by the old Governor of the Dutch colony of New York, more that 200 years ago, and is still standing in fine vigor, on what was once his farm.

The altitude attained by some species of trees is wonderful. Half a century ago, single specimens of white pine (Pinus strobus) were frequently met with, having a diameter of six feet and an altitude of 250 feet. The sugar pine (Pinus Lambertianas) on the northwest coast of the United States, grows to the height of 250 feet; and the Douglas spruce, (Abies Douglasii,) whose size is gigantic, is not unfrequently met with 300 feet in height of stem. The mammoth redwood tree of California, (Sequoia gigantea,) has widely attracted public interest on account of the enormous dimensions of its stem; it has reached the altitude of 400 feet. And the diameter of the famous "original big tree" was 23 ft. 1 in., inside of the bark, which was two feet thick. The blue gum of Australia, (Eucalyptus globosa,) produces a monster stem. Walter Hill, an English botanist, found the blue gum in the interior of Australia, measuring at three feet from the ground 160 feet in circumference, and 80 feet in girth at 56 feet from the ground.

But there is a limit (from their peculiar structure) to the age of endogens, for the continual addition of new woody bundles to the interior so much compresses those which were previously contained in the stem, that they are no longer pervious to fluid, and the tree dies. Nature, it is true, sometimes provides a remedy for this in the splitting of the hard envelope, which allows the interior to dilate; and this is being successfully imitated by art-vigor being restored to the palm when languishing, by splitting down the exterior of its stem with a hatchet.

The products of the stem have always been a very large factor in the commercial transactions of nations. Thus we find in the earliest records, the value that was placed upon shitțim, sandal and cedar woods, and fabulous prices were paid for gums, frankincense and myrrh, showing that the addition of fragrant odors was regarded as rendering the sacrifices offered to the Deity more acceptable. In more modern times, the trade in perfumed bark and wood has been simply immense. In some trees the aromatic principle is strongest in the barks, as cassia and cinnamon, the sassafras of Tasmania, in the atherosperma, moschata, croton cascarilla, and the Eleutheria of the Bahamas. The Ocotea aromatica, from New Caledonia, possesses a strong sassafras flavor. There is also a very fragrant bark yielded by the Alyxia aromatica, of Java. From Tasmania we have the muskwood, (Eurybia argophylla,) the native boxwood, (Bursaria spinosa,) and the scent-wood of the same island has an odor similar to that of the Tonquin bean. From Tahiti comes the Ixora odorata, with its highly-fragrant wood. In Australian woods the scented myall (Acacia homalophylla) has an intense and delightful perfume of violets, and the Eucalypti furnish not only most fragrant woods, but also timber of fine and elegant colors. In fact, when it comes to beautiful

woods, irrespective of perfume, the whole world is made tributary, and many yet remain unnoticed because they have not yet become fashionable. In this respect the forests of the United States will be found a mine of wealth, to be worked in the future. We have all the useful, and yet we do not lack for beautiful woods, for ornamental work; the cabinet cherry, curled and birdseye maple, honey locust, and zebra wood, do not make up the list, for we have the black walnut, the prince of cabinet woods, which has long ago taken the palm from mahogany. Our list of building woods is not a large one. Headed by the white pine, whose billions of feet of lumber freights tens of thousands of long railway trains, and covers thousands of acres of river and lake surface, it embraces the building and the cabinet lumbers, the implement and the machine maker's strong timbers, the wheelwright's material, the cooper's stuffs, and the material for the innumerable small-wood manufactures, down to the fine boxwood block upon which the skilled wood graver cuts his lines.

The stem has few diseases, and these few are produced by different causes, such as wet, undrained soil; sudden and violent changes of temperature during early fall; severe pruning of a barbarous character; and injuries received from the whiffle-tree, and inroads of cattle. The pear blight is one of the most formidable diseases with which the pear culturist in Kansas has to contend. With a very few exceptions every variety of this luscious fruit is liable to its attacks. Whether it is caused by the sun, the atmosphere, insects, or fungi, remains in doubt, some cases in various localities favoring one opinion, some another. The venerable Dr. Howsley we think gave the correct opinion in his valuable paper read at the Emporia meeting of this Society. This paper will be found at page 80, Vol. VI, of the Transactions of this Society. Every member should read this paper, and re-read it, and ponder it well. It will amply repay the labor. This disease appears in the trees at different seasons of the year. In February, 1877, it was distinctly seen that all our finest varieties were killed with the blight. It attacks the trees also at different periods during the growing season, and is generally seen in the young, growing parts first. We find that those varieties which mature their wood growth in September, and cast their foliage early in October, are untouched by this disastrous disease. Sun-scald in the stem never occurs in fruit-bearing trees where the trunks are well shaded by the branches above. It is always seen in orchards where the trees are trimmed to tall bare stems. Where it appears, the only remedy (and a very simple one) is to pare off the dead bark, apply a plaster made of equal portions of cow-dung and clay, and cover with a coarse cloth. All our stone fruits are more or less liable to the malady called gum. It is probable that the presence of this disease here in the West is owing to the rapid and violent changes which take place in the winter and spring months, deranging the flow of the sap, and causing it to accumulate in masses; it is also owing in some measure to the bark of the stem not yielding naturally to the growth of the wood.

The cherry tree has a very powerful bark, unyielding in its nature. We have often seen about a foot or more of the stem of the tree several inches smaller than the parts above and below it. These are cases of obstinacy in the bark to expand, and can easily be remedied by cutting longitudinal incisions on the contracted part of the stem. But the great cause of this disease is the vandal practice of severe pruning, by too many of our orchardists, who, with pruning knife and saw, denude their trees of those very parts which are all required for the successful issue of those wonderful processes which Nature is carrying on all around us in the garden, orchard and grove.

The stem of the tree has many insect enemies which have seriously injured and destroyed thousands of trees in our State. We refer our brother horticulturists to the able and exhaustive report of G. C. Brackett, in Vol. VIII, page 202, of the Transactions, for information concerning these insect pests. But if insect enemies have injured "their thousands," there are three animals belonging to the natural order Rodentia, which have destroyed their "tens of thousands." We refer to the American hare, (Lepus Americanus,) the rabbit, (L. Nanus,) and the common meadow mouse, (Mus cucopus.) Their destructive habits are so notorious that they constitute a theme for discussion at nearly every meeting of this Society. All of which is respectfully submitted.

SELECTION OF THE FITTEST.

BY MARTIN ALLEN, OF HAYS CITY, KANSAS.

We believe it is a well-settled axiom, that "the fittest survives," but this is in the mighty struggle for existence that has gone on continually among all living things, both animate and inanimate, from the beginning up to the present time. Man has aided Nature and himself to some extent in this struggle, by selecting animals, trees, fruits, vegetables and cereals, and in cultivating and distributing them in all parts of the civilized world. Among the very most rude types of mankind only is this struggle of Nature left entirely to itself, unaided in some way.

Many sorts of trees grown from seed vary greatly, probably as much as wellestablished breeds of animals do- possibly more; probably no two are precisely alike. Take, for example, the cottonwood: a quarter of a century ago it was the leading rapid grower among the soft-wooded trees in the prairie regions of Illinois, and we think it has at one time or another risen to this position in each of the prairie States of the great Northwest, it certainly holds this place now on the plains of western Kansas, from whence we write. Unfortunately, science seems only to know two sorts of this tree, their difference being known by the bark of the young shoots, and the indentations in the edge of the leaf. Wood-choppers know two sorts, namely, the white and yellow; and tree vendors talk fluently to their customers about these two sorts, and especially about the great merits of the yellow sort, which they have to sell. The very important fact that these sorts are only known by chopping into their wood and noting its color and quality, seems to be overlooked, for they