III. In the third part of my subject I am to compare the vegetation of the line of the river Congo with that of other equinoctial countries, and with the various parts of the continent of Africa and its adjoining Islands.
The first comparison to be made is obviously with the other parts of the West coast of equinoctial Africa.
The most important materials from this coast to which I have had access are contained in the herbarium of Sir Joseph Banks, and consist chiefly of the collections of Smeathman from Sierra Leone, of Brass from Cape Coast (Cabo Corso), and the greater part of the much more numerous discoveries of Professor Afzelius already referred to. Besides these, there are a few less extensive collections in the same herbarium, especially one from the banks of the Gambia, made by Mr. Park in returning from his first journey into the interior; and a few remarkable species brought from Suconda and other points in the vicinity of Cape Coast, by Mr. Hove. The published plants from the west coast of Africa are to be found in the splendid and interesting Flore d'Oware et Benin of the Baron de Beauvois; in the earlier volumes of the Botanical Dictionary of the Encyclopèdie Méthodique by M. Lamarck, chiefly from Sierra Leone and Senegal; in the different volumes of Willdenow's Species Plantarum from Isert; in Vahl's Enumeratio Plantarum from Thonning; a few from Senegal in the Genera Plantarum of M. de Jussieu; and from Sierra Leone in a memoir on certain genera of Rubiaceæ by M. de Candolle, in the Annales du Museum d'Histoire Naturelle. Many remarkable plants are also mentioned in Adanson's Account of Senegal, and in Isert's Travels in Guinea.
On comparing Professor Smith's herbarium with these materials, it appears that from the river Senegal in about 16° N. lat. to the Congo, which is in upwards of 6° S. lat., there is a remarkable uniformity in the vegetation, not only as to the principal natural orders and genera, but even to a considerable extent in the species of which it consists. Upwards of one third part of the plants in the collection from Congo had been previously observed on other parts
