454 SCIENCE PROGRESS. 



analysis of the composition of the vegetation in each. The 

 peculiar species are as 2*6 to I, 2*3 to 1, and 2*4 to 1 

 respectively out of the total number of species known from 

 each region. 



It should be added, moreover, that Mr. Baron finds 

 that the floras of the eastern and western regions differ 

 very widely, which he explains by assuming great age for 

 the elevated central region dividing the two. He states 

 that apart from 100 species which are common to all three 

 regions, only 128 are common to the eastern and western 

 regions. But it would appear the diversities are largely 

 specific rather than generic, and no greater than those 

 existing in contiguous valleys of the great mountain masses 

 of Eastern India and Western China. 



Passing from statistics to the composition and affinities 

 of the endemic element in the flora of Madagascar, we 

 approach a more interesting subject. It is convenient to 

 discuss this in relation to the rank of the groups, whether 

 ordinal, generic, or specific. As already mentioned, the 

 only group of plants endemic in Madagascar to which 

 ordinal rank has been assigned are the Chlaenacese. 

 Whether regarded as an order, or as a tribe of the 

 Ternstrcemiaceae, as proposed by Baillon (25), there is no 

 doubt that they form a group of very curious genera, 

 mostly characterized by having an involucre, or epicalyx, 

 and a cylindrical or cup-shaped organ called a disk, within 

 and upon which the stamens are seated. They are shrubs 

 and trees ; one species being as much as a hundred feet 

 high. Seven genera have been found, and about twenty- 

 eight species. According to Baron, the majority of them 

 are found in the eastern part of the island, and the genus 

 Rhodolcena is confined to that side. The only species of 

 Sclerolcena inhabits the north and north-west, and the four 

 species of XerocJilamys occur on the hills and mountains of 

 the interior. Leptolczna panciflora, an eastern member of 

 the order, "is a hard- wooded tree, from the trunk and 

 branches of which, at a certain season of the year, there is 

 a ceaseless dropping of water, sufficient indeed to keep the 

 ground quite damp ". 



