Page:Popular Science Monthly Volume 15.djvu/662

 by a young slave, Edmond Albius, in the service of M. Ferréol Beaumont-Bellier. Albius bad noticed bow his master, who had considerable acquaintance with natural history, used to produce hybrids by cross-fertilization of the various flowers in his garden. Having made like experiments himself, the young slave observed that, on touching with a spine of palm the flowers of the vanilla, two little yellow bodies contained within changed position, and that fructification resulted from the contact. A new branch of commerce was henceforth created, and vanilla-beans, previously very dear, were quickly much lowered in price.

The vanilla is a climbing plant with pulpy stem, but it can reach the tops of high trees. In our greenhouses it attains proportions sufficiently great to enable us to judge of its appearance. Its stem, which can be easily made to ramify, is from two to three centimetres in diameter. Its leaves are arranged in two rows, or are alternately distichous, as the botanists say. In size they vary from fifteen to twenty centimetres, and they are slightly twisted on their short petiole, so as to appear to be inserted obliquely. This torsion seems to be produced by the need for the leaf of having its upper face always turned toward the light.

Besides the roots at the base of the plant and fixed in the soil, a multitude of adventitious aërial roots start from the stem or the branches, after the plant has reached a certain size. These roots hang free so long as the stem rises vertically, but become fixed in the soil when the stem touches the ground. They start from the level of a leaf alongside of a tendril, with the aid of which the plant climbs trees.

The stem, which in the interval between two leaves takes a direction the reverse of that taken in the next interval—a zigzag—is charged with a thick vesicating juice, which on being applied to the skin produces a blister.

The flowers appear in clusters at the axils of the leaves, and are numerous; but care is taken to leave only a small number of them on the plant when it is desired to have fine fruit. These flowers last for only one day, and fructification, in order to be successful, should take place in the morning. The instrument used for this operation is a pointed piece of bamboo. A skilled man can fecundate as many as one thousand flowers in a morning. One month after fecundation the fruit has attained its full size, yet it has still to remain on the plant six or seven months more before it reaches perfect maturity.

The flowers of the vanilla have none of that richness of color so common among orchids. They are whitish or yellowish, according to the species to which they belong. Apart from those which are cultivated on account of the perfume of their fruit, the others possess only a purely botanical interest.

A physiological detail that is worthy of mention is the attraction of the stigmas of these flowers for the pollen offered to them. Neumann the younger had frequent occasion to notice this while