OF CENTRAL AFRICA. 273 



regard the ovarium as having in all cases only two placentae, 

 and therefore formed of two pistilla or carpella. But to 

 this, which is certainly the more usual number, there are 

 many exceptions. These exceptions occur chiefly in the 

 genus Capparis, which, as it is at present constituted, 

 includes species differing from each other in having an 

 ovarium with from two to eight placentae, and consequently 

 composed of an equal number of pistilla. Capparis spinosa 

 is the most decided instance of the increased nmnber of 

 placentas, and this, as well as some other nearly related 

 species, are also remarkable in having septa subdividing the 

 placentas, and uniting in the centre of the compound 

 ovarium . 



In the herbarium there are 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 mouo- 

 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 Polauisia, uniting all the 

 Cleomes 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, 

 Avhose only congener is placed in a second section. 



Gynandropsis 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. pe7itapliyUa 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 period. To this mode of aestivation [ssi 

 of petals, which has never before been noticed, though it 

 equally exists in Crateva and in Resedaceae, I shall apply 



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