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Of all those plants, one only, is indiginous to our continent; and this is so remarkable in its economy, and so important as an article of food, that we shall notice it as an illustration of the effects produced by change of climate upon the vegetable kingdom.
In the United States, the region of the most perfect developement of Indian Corn, [Zea Maiz] may be considered as extending from about thirty-three to thirtynine degrees of latitude; it is however, highly productive on both sides of this belt. But as we proceed north, from about latitude thirty-nine, the plant gradually becomes smaller, and the size of the ear diminishes in proportion. This decrease in the size of the plant, for the first two or three degrees, is compensated by the increased number which may be grown upon a given quantity of ground; but as we proceed still further towards the north, the number and size of the grains produced by a single plant, become so much diminished, that the increased number of plants, fail to make the crop equal to that of the true corn growing region; and thence, as we proceed north, the value of the plant rapidly decreases. But still it continnes to accommodate its habits to the climate, and to produce seed, until loosing its large and beautifully developed proportions, it returns to what may be called a grassy state, and produces the seed upon the top of the stem, instead of the ear, which in a more favorable climate shoots out from about the middle of the plant. These changes are the effects of climate merely; but the general economy of the plant is remarkable in many other respects. It delights in a deep and well pulverized pasture, and sends out its roots to feed at a great distance from the stem; from these roots, innumerable small fibres, or radicals branch off, and take complete possession of the whole mass of pulverized earth near the plant, except a small portion at the surface. When the plant is in this condition, one might conclude, that if these roots were broken up by the plough, it would perish; but as they can only perform the office of feeders at their extremities, when that part of the earth nearest the plant has been once completely overrun, it ceases to contribute to its support;
and hence it is important to break these roots, that the plant may send out a new race of feeders, into a new pasture, improved by the chemical effects produced by pulverizing the soil.
The plant requires a high degree of temperature to stimulate its developement; but it takes care to protect itself from the heat of a burning sun; and its arrangements for keeping cool, during a hot day, is most admirable. In the first place, the stem is very succulent, and contains a large quantity of fluid; and to prevent this fluid from evaporating too rapidly, a leaf is attached to each joint, the footstalk of which, forms a wrapper that encases the stem to the next joint above, leaving a small space between this wrapper and the stem, which forms a reservoir for holding water; the leaf is smoth upon the upper surface so as to reflect the heat, and being depressed in the centre, and more elevated at the extremity than at the base, it serves as a conductor to the dew which is formed in globules upon the smooth surface, and carries it to the reservoir at the base of the leaf. By this admirable contrivance, if the dews have been copious during the night, a sufficient quantity of water will have been collected, to supply the plant with moisture, and to keep it cool by evaporation during the heat of the day; and thus it rejoices in comfort while other plants are drooping around it.
From these causes, it is better calculated to resist draught or to recover from a bad state of cultivation, when the cause is removed, than perhaps any other plant. When the grain has matured, the ear, which was erect while growing, becomes pendant, and being covered with a strong husk, is protected, as well from the rains, as from the ravages of small animals and birds; thus evidently proving that the economy of the plant has reference, not only to its growth, but to the preservation of its seed
When these, and many other remarkable traits, in the character of this plant are considered, the mind is so forcibly impresssed with the obvious design evinced in the arrangement of all its parts, that we are almost ready to conclude that it is a thing of intelligence, rather than a mere plant.
From these peculiarities in its economy, and its wonderful elasticity in recovering from adverse circumstances, it is the most certain of all crops known to man; and it may safely be predicted, that if planted in due season, and cultivated with skill, that a crop throughout the corngrowing region of the United States, would not fall twenty per cent. below the general average, once in a series of one hundred years. And when we consider that it is abundantly more productive than the other grainbearing plants, and that a greater number of crops may be raised upon the same ground, in any given series of years, we must conclude that the middle region of the United States is capable of feeding a much larger number of people with bread than any other country of eqnal extent of territory upon the globe. This gives to the corn-growing region of the United States an importance which has not usually been attached to it; for the fact of this being the great provision region, and located in the centre of the Union, must, in time, regardless of artificial circumstances, give it the control, not only of the policy, but of the capital and commerce of the whole country; for labor will sooner or later perceive and appreciate the advantages of locating as near as practicable to the point where the necessaries of life are produced.
We have digressed somewhat from our subject; but the article of Indian corn is so purely American, and the region of its production so peculiar in its relation to the other parts of the Union, that we felt almost compelled to notice it, as one of the prominent elements of American greatness.
The cotton plant, (Gossipium,) is another remarkable instance of the effects produced upon plants by transferring them from one climate to another. This plant is perennial in the torid zone, and grows there to a sufficient size to be denominated a tree; as it is removed towards the north, it gradually diminishes in size, and after passing the latitude of about thirty degrees from the equator, it changes from a perennial to an annual plant; and losing the fibrous tissues which belong to the tree, it becomes herbaceous.
As it progresses towards the north, it continues to diminish in size, until reaching the latitude of from thirtyseven to thirty-eight degrees, it ceases to reproduce itself. In tracing its habits and economy we discover that in the torid zone, where the life of the plant is protracted to many years, it does not seed so abundantly as it does when, by change of climate, it becomes an annual plant; for the reason that there is less necessity in the former case of making provision for the perpetuation of the species. Furthermore, in the torid zone there is no necessity of protecting the seed when ripe, so as to preserve them until a particular season of the year; therefore, they are smooth, and, with the fibre, which is very loosely attached to them, fall from the pod almost as soon as it is open. When the plant becomes annual, the fibre closely adheres to the seed, and serves as a protection against moisture, and in the more northern parts of the cotton-growing district, the seed, with the fibre attached to them, remain in the pod all winter, and are thereby preserved in a sound condition. Thus we perceive a series of calculations, apparently the result of a reasoning faculty, all tending to the protection of the plant against the change of climate. Like Indian corn, it has its region of greatest productiveness; which, in the United States, extends from about latitude thirty-one to about thirty-five north; and it may also be observed, that, like Indian corn, in another respect, the further north it is planted, the greater is the number of plants which are necessary to be grown on a given quantity of ground, to insure a profitable crop. No other material, so suitable for clothing, which has yet been discovered, can be produced in so large a quantity, upon a given area of land, as the article of cotton; and in no other country are the seasons so favorable for its production, as in the United States, except perhaps in some parts of South America. This is another important element of our national greatness; and it is worthy of observation, that the regions of indian corn, and of cotton, are not only in close proximity, but, that they run into each other, and give us the control of the two greatest staples known to man, the one to feed, and the other to cloth, the inhabitants of the earth.
The Irish potatoe, (solanum tuberožum) presents another remarkable instance of the effects produced upon plants by a change of climate, This plant is of little value within the tropical climate of America, where it was first discovered by Europeans; but when transferred to, and cultivated in colder climes, it becomes one of the most prolific food bearing plants known to man. It is a fact generally known to the people of the United States, that the potatoe gradually improves in quality as we proceed from the gulf of Mexico to the northern Lakes. This improvement in the quality of the potatoe, we suppose to be produced by the economy of the plant in protecting the tuber from the greater degree of cold in the more northern latitudes. It is a common practice with the planters of the south to procure seed potatoes from the more northern districts; and no one doubts, that, the first crop from these seed is much better than potatoes grown from those raised in the south. The potatoes raised the first year from northern seed are considered but little inferior to those produced further north; after this they rapidly decline, and in two or three crops become adapted to the climate and are no better than other southern potatoes. This plant propogates from both the flower seed and the tubus; this provision in its economy evinces the extreme care which nature has taken to ensure the perpetuation of its species against accidents which might possibly happen to the seed produced from the flower. The inherent, and natural mode of propogation is by the flower-seed, and the tuber is a mere adjunct, to be used as an expedient in case the flower seed should fail; and is to be considered simply as a part of the old stock.— Hence, in time, the offspring from the tubus is liable to decay, upon the same principle that a particular variety of fruit decays by being propogated for a long time by grafting.
From this view of the economy of the plant, we are naturally led to submit a few suggestions upon the subjet of disease known as the "Potatoe-rot." When we subject a plant to cultivation, it is important to study its economy, and understand its native or normal habits; to the end that we may give them the proper direction without do