be that of the valvular æstivation of the calyx; for several, at least, of the genera at present referred to Tiliaceæ, in which this character is not found, ought probably, for other reasons likewise, to be excluded from that order: and hence perhaps also the Chlenaceæ, though nearly related, are not strictly referable to the class Malvaceae, from all of whose orders, it must be admitted, they differ considerably in habit.
LEGUMINOSÆ. According to Baron Humboldt,[1] this family, or class, as I am rather disposed to consider it, constitutes one twelfth of the phænogamous plants within the tropics. Its proportion, however, is much greater in Professor Smith's herbarium, in which there are 96 species belonging to it, or nearly one sixth of the whole collection. And ample allowance being made for the lateness of the season when the collection was formed, which might be supposed to reduce the number of this family less than many of the others, Leguminosæ may be stated as forming one eighth of the Phænogamous plants on the banks of the Congo. In India, it probably forms about one ninth, which is also nearly the proportion it bears to Phænogamous plants in the equinoctial part of New Holland.
I have formerly proposed to subdivide Leguminosæ into three orders.[2]
Of the first of these orders, MIMOSEÆ, there are only 430] eight species from Congo, seven of which belong to Acacia, as it is at present constituted; the eighth is a sensitive aculeated Mimosa very nearly allied to M. aspera of the West Indies, as well as to M. canescens of Willdenow, found by Isert in Guinea; and perhaps is not different from the species mentioned by Adanson as being common on the banks of the Senegal.
Of the second order, CÆSALPINEÆ, the collection contains 19 species, among which there are four unpub-
