To give the reader a better idea of adaptations and of their importance to living creatures, it will, perhaps, be as well to devote some space to an account of examples of them. Amongst organisms that attract our attention by their pleasing aspect, there are not many that can rival flowering plants. Every one admires the great beauty of the blossom of orchids. There can be no doubt that these flowers have not been developed to satisfy the æsthetic tastes of man, for the simple reason that orchids existed for a long time before man’s appearance. Among orchids there is one which, for more than half a century, has been cultivated by man in many tropical countries. This is the Vanilla, the fruit of which produces one of the sweetest of spices. In former days the pods of only the wild vanilla, which is an undergrowth of the forests of Mexico and South America, were gathered. But the employment of vanilla to flavour chocolate has rendered its artificial culture lucrative; consequently the plant has been transported to several warm countries where it could be acclimatised. It has flourished and borne numerous blossoms, but it has never produced fruit from which alone the aroma is obtained. As the question of the sterility of the vanilla was of great practical interest to the cultivator, the matter was investigated, and it was found that the flower remained sterile because the female and male parts could not come in contact. The pistils and stamens of the flower are well developed, but between these sexual organs is a membrane which prevents fertilisation. After this discovery was made, the idea occurred that the pollen of the vanilla flower might be transferred artificially to the stigma of the pistil so as to bring about “artificial” fertilisation. A young black slave, Edmond Albius, a native of Réunion, discovered in 1841 a practical method by which the male and female elements of the vanilla could be put in contact; and from this discovery there came a great extension of the cultivation of the orchid in many countries. At a certain period a small bamboo point or the tooth of a comb is introduced into the vanilla flower, and in this way, in a short time, a quantity of flowers may be fertilised and so made capable of bearing mature pods.[29] In the original home of the vanilla the intervention of man is unnecessary. In Guiana and Mexico fertilisation of the flower is the work of small bees (of the genus _Melipona_). They frequent the vanilla flowers to extract nectar, the material of their honey. Small humming-birds also hover over the vanilla blossoms, and by introducing their bills into the sexual organs of the flowers bring about contact of the male and female elements. Sterility of the vanilla in the countries to which it has been introduced, before the employment of artificial fecundation, is easily explained by the fact that in these countries there are no insects nor humming-birds capable of transporting the pollen.