The value of the rubbers of different trees is by no means the same. That of the Hevea is much the most valued, and consequently this tree is the most extensively cultivated of the four mentioned. This seems to be due to the fact that this rubber contains less resin than do the other rubbers. In Hevea there is also a perceptible difference in the quality and quantity of latex obtain able from different trees.
Culture.
As there are some important differ ences in the way that each kind of tree requires to be treated, both in the mat ter of cultivation and preparation of the rubber, it will he advisable to treat of each kind separately. Because of its importance, and inasmuch as some of the practices employed in raising Para rubber apply to all the others, or will serve to illustrate the general principles, this species is discussed at length.
Para rubber (Hcrea Brasiliensis). Figs. 790 793.
The Para robber is a native of the tropical forests bordering the Amazon river and its tribu taries, where it grows in a damp, hot climate, with a heavy rainfall, and with no distinct dry period. It is therefore suited for those parts of the world which lie close to the equator, and are known as the tropical rain-forest region. It thrives in the West Indies. The temperature at which it grows shows a mean annual of 78° Fahr ; mean maximum, 87° Fahr ; mean minimum, 69° Fahr ; extreme maxi mum, 93° Fahr ; and extreme minimum, 62° Fahr.
The seed.--This tree is nearly always grown from seed, for, although it is possible to raise it from cuttings, this is not to be recommended. The seeds in adult trees are produced more or less throughout the year, but the main crop is ripe in August (in Trinidad always in September and October). The seeds are about an inch long, oblong-rounded, with one side slightly flattened, dark brown marbled with silver. They vary in size, some of the finest trees giving very small seeds. They are produced in a large, woody, three-celled capsule, which when ripe explodes violently, throwing the seeds.
The seed should be planted as soon as possible after it ripens, as its vitality is of short duration, and, unless specially treated, it dies within a week. Seed sent from a distance, which has been long on the way, should be soaked in water for a day before planting.
The nursery (Fig. 792).—Nursery-beds are made in moderately moist, rich soil, carefully worked. The seeds are placed in rows about six inches apart, on the flat side, and pressed into the soil for about half their depth. In some regions they are not covered with earth. It is advisable at first to cover them with a light shade of leaves or branches, about a foot above the ground. The seed germi nates very quickly. The plant can be removed to the plantation when it is about a foot tall, which will be six or eight months from the time of plant ing the seed. However, it may be kept in the nur sery till much later, as it is very hardy and bears transplanting at almost any age. It is advisable to keep it longer in the nursery when the plantation is liable to the attacks of grasshoppers or slugs, or where dear or other wild beasts are likely to attack the young plant. In such cases the taproot should be cut off, and, if the young plant is over twelve feet in height, the top should also be removed with a clean cut at eight to ten feet from the ground.
Young plants of Hevea should be potted in bamboo joints as soon as they can be safely handled ; and the same applies to all the species. In the bamboo pots the young plants can await time or season for planting better than if grown in nursery beds, and will stand transport better. However, they should not stand too long in these pots, or their routs may become cramped and hinder future growth. (Hart.) The plantation.—The soil in the plantation should be rich alluvial fiat, free from salt-water and well drained. Rocky or very sandy soil should be avoided. The ground should be cleared of trees and bushes by felling and burning, and the young trees should be planted about twenty-five feet apart.
Growth.—The growth in a suitable locality is very rapid, and the young trees should be about fifteen feet tall in a year and a half, and should attain their full height of sixty feet in about eight years. If they grow very tall and slender it is advisable to top them at about eight or nine feet from the ground. For the first few years the ground should be cleared of weeds from time to time ; afterward it is less necessary, as the trees will shade out the weeds. No further cultivation is required.