Popular Science Monthly/Volume 30/November 1886/The Hickory-Nuts of North America
|THE HICKORY-NUTS OF NORTH AMERICA.|
IT is a favorite pastime of our country population during the long winter evenings to gather round the fire and crack and eat hickory-nuts. It is an amusement, too, peculiarly American, and for the simple reason that in this country alone are the nuts to be had in any abundance. Perhaps, where almonds or English walnuts are equally common, cracking hickory-nuts is superseded by a resort to these other fruits. They, however, are much easier to open than the hickory-nut, and with thinner shells are readily cracked at the table. But in America, in those districts where the peanut does not take the place of other nuts, the cracking of the hickory still continues. Whether it be the pecan of Texas and Illinois, or the shell-bark or mocker-nut of the Central or Eastern States, the amusement is the same. They are the best nuts the forests of North America produce, and some of them are thought to be superior in flavor to the much-esteemed English walnut.
Year after year have hundreds and thousands of bushels of the shell-barks, the hickory-nuts par excellence, been gathered in various parts of the country. Among these, few can have failed to notice the many differences they present. Some are small and nearly round; some are long, narrow, and angular; some have thick shells, and some thin ones, as any one who has cracked his fingers along with the shell can bear witness.
According to evolutionary doctrines, variability in an important feature is an indication either of a low state of development, or that the organism is in a state of advancement. Various facts show the latter to be the case with the shell-bark hickory. The first stages of the onward march must be sought far back in prehistoric times, for it boasts an ancient if not an honored lineage. Before the hairy mammoth roamed the forests of the Ohio Valley; before the soil of Louisiana was yet above the ocean's waters; before the Ohio had become tributary to the mighty Mississippi; before even the Rocky Mountain range had been elevated above the waste of waters, the ancestors of this hickory flourished in the land. But, before we study the ancient hickories, let us examine the living trees and note their peculiarities.
Were the same observers who saw the differences in the size and shape of the nuts of the white shell-bark to direct their attention to the husks of that fruit, they would find much variability there also. But these are secondary considerations with the nut-gatherers. If a nut falls to the ground with the husk intact, the nutter gives it a kick with his boot-heel, or a blow with his stick, and separates the husk into its component parts. For this outer covering divides readily along the sutures and falls into four pieces. Sometimes the four form a nearly perfect ball; sometimes they are long and taper to a point; occasionally, three pieces will serve the purpose of four, but they are all dark green or brown on the outside, white with streaks or veins of brown inside, and they vary from a quarter to half an inch in thickness.
Yet another thing will the nutters notice, and that to their disappointment and disgust. This is the number of nuts having neatly cut, round holes in the shell. Out of these there will often be seen protruding the white body of a well-fed worm, which has been growing in size and strength since the egg hatched in the young nut. The grub grew with the growth of its house; it found an abundant store of nutriment, and it attains a size which makes it a matter of wonder how it manages to escape from the neat little round hole it has cut in the thin white shell.
Such is the fruit of the white shell-bark. The tree which produces it is equally interesting. The common name of shell-bark or shag-bark tells at once its most remarkable characteristic, and one by means of which it is most easily and readily recognized. The bark, instead of being securely attached to the trunk as in most trees, breaks loose from it and hangs in strips, fastened sometimes in the middle, sometimes at the upper and at other times at the lower end. The whole trunk thus presents a shaggy, rough appearance, and in some cases resembles the ragged ends of an ill-laid and worn-out thatch. This feature is only to be observed in trees of more than ten years of age, younger ones showing indications of what is to come.
It is a majestic tree, eighty or ninety feet in height, straight and without a branch for sometimes sixty feet, and then spreading out its bushy head. In the spring the young leaves make a very rapid growth, attaining a length of twenty inches in a short time. These leaves are divided into five leaflets, four being in two opposite pairs, and the fifth placed at the end. Each leaflet tapers to a sharp point and has saw-like teeth on the edges. The flowers are small, green, and form long, pendent catkins, arranged in bunches of threes, with the fertile or pistillate flowers at the base. The pollen is produced in immense quantities, and conveyed from the stamens to the pistils through the agency of the wind. The species is widely distributed over the country, ranging from the St. Lawrence Valley and Southeast Minnesota on the north, to Florida and Texas on the south. This extensive dispersion is perhaps one reason for the variability the nut presents, as under varied conditions it assumes diverse forms.
One of the nearest relatives of the white shell-bark is the thick shell-bark. In this species the nut is very large, has an extremely thick husk and shell, and a small but sweet kernel. The husk separates into pieces, the flowers are alike, and the bark exfoliates in much the same way in both. There are, however, often seven instead of five leaflets, but they have a pointed apex and serrate edges. The tree is not so widely distributed over the country, as it is found mainly in Fig. 2.—Thick Shell bark (Carya sulcata). the Mississippi Valley, north of the Ohio River. The very heavy shell, requiring severe blows with a hammer to crack, makes the reason for this more limited diffusion obvious. Depending almost solely on rodents for its dispersal, the size of the nuts preventing the wind from carrying them to any distance, the heavy shell makes it a most difficult task for the gnawers to penetrate to the kernel within. It will be readily understood that the thinner and yet sweet-kerneled nuts will be chosen in preference. And while mice and woodchucks and chipmunks and squirrels will lay up stores of the thin-shelled nuts, often carrying them long distances, the heavy-shelled ones will seldom be molested, but remain where they fell near the parent tree. The heavy shell would, again, be an impediment to germination, and thus fewer individuals would grow, and those which did sprout would have little chance of attaining maturity while overshadowed by the older tree. Thus we have a simple explanation of the fact of the limited distribution and the small number of individuals in any given area.
The near ally of this species is another heavy-shelled sort, the mocker-nut, which has a much thinner husk and yet a thick shell.
The nut is quite large, intermediate in size between the white and the thick shell-bark, of a yellowish color and a sweet kernel. The bark has not the scaling propensity, but the flowers and the leaves are quite similar. Its distribution is wider than the thick shell-bark, but it is still limited. One peculiarity is observed in all three species, and that is the great variability in the shape of the nuts, a feature that is much less marked in all the other sorts.
The white shell-bark occupies a sort of intermediate position in the genus. On one hand are the thick-shelled species already noted, forming one line, and on another line are two species marked in other ways, but mainly by a difference in the kernel. While in the three already described this is sweet and palatable, in these other two it is bitter and uneatable. These have, also, thin instead of thick husks, and they separate only about half-way down instead of into four distinct pieces. The shell is thin, so much so in some cases as to be easily crushed in the fingers. In size, shape, and markings there is none of the variability of the shell-bark. Of the two species the bitter-nut is
the more common. The bark is close; the tree grows to be forty or fifty feet high, the shell is smooth, sharp-pointed, and marked with lines, while the kernel is so bitter that it is rejected by squirrels and other animals as long as other food can be obtained. The leaflets are small, from seven to nine in number. Its distribution is limited to nearly the same area as the mocker-nut, namely, the valleys of the Ohio and its tributaries, Minnesota, Kansas, and Western New York.
|Fig. 5.—Water-Hickory (Carya aquatica).||Fig. 6.—Small-fruited Hickory (Carya microcarpa).|
The water-hickory has many of the same features, but the shell of the nut is thinner still, and the kernel yet more bitter, while the tree is confined to the swamps of Carolina and Georgia, where it is by no means common. Its nut is of a reddish color, and more or less angular.
On a third line running from the white shell-bark are three other species. One of these is the small-fruited hickory, in which the husk and the shell are both thin, and the kernel, though small, is eatable. It is closely allied to the white shell-bark, and by some considered a variety only. A second species is the pig-nut, which has a thin husk but a thick shell. The kernel is small, and, though agreeable at first, soon becomes bitter and disagreeable. It is never eaten by man, but
|Fig. 7.—Pig-nut Hickory (Carya porcina).||Fig. 8.—Nutmeg Hickory (Carya myristicæ-formis).|
used to feed hogs, or left for the wild animals. This nut is somewhat variable in shape, sometimes being distinctly pear-shaped and then again round. Michaux says that the same tree yields nuts as large as the thumb and others as small as the little finger. The third species in this same line is the nutmeg hickory, which has a somewhat rough husk, with a smooth nut, lined with streaks of white, and a shell so thick as to constitute one half of the whole nut. The kernel is inferior even to the pig-nut hickory.
If all these species were to be arranged so as to show their affinities, something like the following diagram would result:
|Small-fruited hickory,||Thick shell-bark,|
From facts already given it will at once be apparent that two features in the nuts are correlated. The thick-shelled nuts have sweet kernels, though they differ in edibility, and the thin-shelled ones are invariably bitter. Thus the sweet ones protect their kernels by incasing them in hard shells—a precaution unnecessary for those whose kernels are bitter, because they are protected by this feature alone.
There remains, now, one species to be considered, and that is the pecan. While the white shell-bark seems to occupy a central place among the species, the pecan is intermediate between the hickories and the walnuts. These two genera, Carya and Juglans, as botanists know them, constitute the main part of the order to which they belong. When two genera are as closely allied as these are, an evolutionist accords a common origin to both. In fact, the difference between the two is a technical and comparatively an unimportant one. It is the presence in the hickories of staminate flowers in clusters of threes, while in the walnuts there is but one; and by the more or less complete separation of the husks of the hickories into four pieces, while the walnuts have no such division.
Now, the pecan is allied to the walnuts by the number of its leaflets (thirteen to fifteen, while the walnuts have, in one species, seven Fig. 9.—Pecan (Carya olivæfarmis). to eleven, and in others fifteen to twenty-one), and by having its catkins separated at the base instead of being united. And it agrees with the hickories in having three catkins instead of one, and by the husk of the fruit separating into four pieces. The kernel is very sweet, the husk is thin, and the nut smooth and rather thin-shelled. The peculiar feature of a bitter division between the two halves of the nut is an approach to those hickories having a bitter kernel: while the hard shell and the sweet kernel ally it to the shell-bark. The tree is confined now to the States near or bordering the Mississippi River, and is thus the nearest of all the species to that spot which was once thickly clothed by its ancestors. It is noteworthy, too, that the walnuts approach the same habitat, and in the case of one species extend across the continent to California.
From an aboriginal ancestor which probably possessed a many-parted leaf, and a fruit with an entire husk and a thick shell, there came two branches. One of these, retaining the numerous leaflets, developed a nut with a corrugated shell and a thick, green husk, represented by the living species of walnuts. The other branch gave rise to a species having a nut resembling the pecan, with a smooth shell, and a husk separating more or less completely into four parts. Some of the various stages of development from such an ancestor have probably been preserved to us. The white shell-bark may be regarded as a modified descendant in which the bitter internal division has been lost, and the outer shell strengthened to afford additional protection. The mocker-nut and the thick shell-bark have acquired a still stronger covering to protect them in the same way. The small-fruited hickory is probably a stepping-stone to the pig-nut, with its thick shell and partially bitter kernel; while the thin-shelled bitter-nut and water hickory are other offshoots in which the bitter kernel does away with any necessity for a hard and thick shell.
The geographical distribution of any species or genus is an interesting and important adjunct to its history. At the present day, all the species of hickories are natives of North America east of the Rocky Mountains. Two out of four of the species of walnuts are confined to the same limits; a third is native to California and Mexico; and the fourth, the English walnut, is a native of Persia and the Caucasus. In times past the distribution was far different. "What information we have is derived only from a confessedly imperfect geological record—a record exposed and explored as yet in the Rocky Mountain region, in Alaska, Greenland, and Central Europe. In all of these places species of either the one or the other genus have been found. It is true that the determination of species or even genera is difficult from fragments of leaves, but, as far as is now known, the following are the facts:
During that period of time known as the Cretaceous epoch, a tropical climate prevailed over the whole of the northern hemisphere, even to the pole itself, and probably also over the whole world. During that time forests of trees flourished over the continent of North America, over Europe, and probably Asia also. These forests were, in many respects, similar in aspect to those which at present clothe portions of the Ohio Valley. What species of trees lived in that part of the country north of Virginia and Tennessee and east of the Mississippi, it is now impossible to tell. But west of that river, and over the larger part of the Rocky Mountain region, there grew forests in which poplars, willows, oaks, beeches, sycamores, gums, magnolias, and perhaps walnuts and hickories, were the prevailing types. The remains of all but the last two have been found in the immense series of Cretaceous rocks of the "Western States and Territories, having fortunately been preserved in the deposits of the shallow seas or great lakes which then occupied that part of the American Continent. The genera mentioned are but a few of those of which remains have been found, but they indicate a similarity in the flora then to that of the present epoch. Many of the same genera are found in strata, of presumably the same age, in Alaska, Greenland, and parts of Europe, and these facts indicate not only a similar climate in all these localities, but a similar forest aspect.
In the Tertiary formations, coming after the Cretaceous, the resemblance to modern trees is still more striking. During this later period, that part of the Rocky Mountain region which had before been under water was elevated above the surface, but immense basins remained which were filled with brackish or fresh water. It is in these fresh-water deposits that the abundant remains of ancient forests are found. Many of the same types present in the Cretaceous period are found in the Tertiary in still greater numbers. If there be any doubt about the occurrence of walnuts and hickories in the former period, there can be no question about their being in the latter one. The number of species of oaks, poplars, figs, ashes, magnolias, and many others equally well known, was increased. But we shall here consider the two genera, the walnut and the hickory.
In Europe one species of walnut is found in the Cretaceous rocks, and a doubtful one is mentioned as found in rocks of the same age in America. The lowest series of Tertiary rocks in Europe contains remains of three species, and the upper series of no less than forty-three species. The hickory seems to have appeared in Europe in the middle Tertiary, and in the upper beds is represented by twenty-one species. In America the walnut is well represented in the lowest Tertiary, and increases in numbers toward the top; while the hickory is represented by several species through the whole series. When the living species of these two genera are considered, a widely different state of affairs appears. The forty-three species of walnuts dwindle to one; the hickories are entirely absent, though perhaps represented by three somewhat different genera now growing in Japan and parts of India.
The fact that many genera of Tertiary plants are common to North America, the Arctic regions, and Central Europe, is evidence of some former land connection. This connection was probably at the northern ends of the continents, and it allowed the free commingling of the floras of the two bodies of land. When at the close of the Tertiary vast changes took place in the distribution of land and water; and when a wave of extermination swept over the northern and western portion of this continent, the same disaster overtook the forests of Europe. The eastern half of North America and the eastern part of Asia seem to have escaped the effects of the vast change; for in these two regions are still found the remnants of the previous floras. Europe and the Rocky Mountain region suffered from the throes of mountain-making, and the disastrous effects of these convulsions are shown in the extinction of the luxuriant flora and the varied fauna which had previously existed.
Thus it can be seen that our hickory can boast a pedigree which puts to shame the mushroom-growth of modern days; and, while the descent can not be traced in a direct line through all the intermediate stages, we can safely formulate the main facts. The ancestor of both walnut and hickory orignated toward the beginning of the Cretaceous period. The separation of the two occurred toward the end of the same epoch, and they both spread during the highly favorable period of the Tertiary over the whole country and across the Arctic zone into Europe and Asia. The continental condition of Eastern North America and its lack of large, shallow lakes forbade the preservation of such forms as existed there; and the comparatively small portion of our Western region which has been explored has prevented the discovery of many of the species then living there. Yet there can be little doubt but that, if our knowledge of pre-existing species was sufficiently full, we should be able to trace back to some common ancestor all nine of those species of hickory which now live in our country, and the fruits of some of which annually contribute to the enjoyment of hundreds and thousands of our people.