OF CENTRAL AFRICA. 273
regard the ovariiiin as liaving in all cases only twoplaccntcC, and tliercforc formed of two pistilla or carpclla. But to this, Avliich is certainly the more usual number, there arc many exceptions. These exceptions occur chiefly in the genus Capparis, which, as it is at present constituted, incUides sjjecies differing from each other in having an ovarium with from two to eight placentae, and consecpiently composed of an equal luunber of pistilla. Capi)aris spinosa is the most decided instance of the increased nund)er of placenta?, and this, as well as some other nearly related species, are also remarkable in having septa subdividing the placentae, and uniting in the centre of the comj)ouiid ovarium.
In the herbarium there arc three species of the genus Cleome. Two of these, C. pentaphylla and arabica, are in many respects well-known plants ; the third I believe to be an undescribed species, but nearly related to mono- phylla.
If the very natural group, formed by the Linnean genus Cleome, is not to be preserved entire, its subdivision must be carried much further, and established on other grounds, than has been done by M. De Candolle, whose genera and sections appear to me to have been equally founded on partial considerations. Thus, his Tolaimia, uniting all the Cleomcs whose stamina exceed six, contains in its first section, in addition to the species from which the genus was formed, at least two sets of plants, having very little affinity either with each other or with the original species, whose only congener is placed in a second section.
Gijnandroims also consists of two groups not very inti- mately connected ; the first is composed of species belong- ing to South America, and having the usual aestivation of the family : the second, of which C. pentaphijUa may be taken as the type, is chiefly African, and is readily distin- guished by its very different aestivation, — the great pecu- liarity of which consists in the petals not covering the stamina at any ])eriod. To this mode of aestivation l::i of petals, which has never before been noticed, though it equally exists in Crateva and in Rescdacca', I shall apply
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