TRANSACTIONS OF SECTION D. 725 



Common to the three Regions ....... 73 



„ ,, Eastern and Central 142 



„ „ Western and Central 59 



„ „ Eastern and Western 89 



The taUe (exhibited) shows the Orders most largely represented and their 

 percentage of the total flora of the respective Regions. 



In this table the following facts are prominent. In the lilastern Region the two 

 most abundantly represented Orders are Filices and Leguminoste, but the former 

 are in proportion to the latter as much as 5 to 2. It will be noticed that Filices 

 do not appear in the second or third column at all, the reason being that there is 

 not sufficient data for determining their relative position. Possibly they might 

 occupy the third or fourth place. Neither, for the same reason, do the Graminese 

 appear in the third column. In the Western Region the Leguminosse stand at the 

 head of the list, and this order is followed by Euphorbiacese, but the difference 

 between the two is very great, the proportion being more than 5 to 1. The table 

 shows that 24'6 per cent, of the flora of the Western Region consists of Leguminosse. 

 The Compositse form only 3 per cent, of the flora. In the Central Region, on the 

 other hand, the Compositas stand head of the list, with a percentage of 12-2. 

 Rubiacese do not appear in the column representing the Western Region at all. 

 They, in fact, only form about 2 per cent, of the flora. The Eastern, Central, and 

 Western Regions therefore might, if we take the most largely represented Orders 

 into account, be fairly called the Fern Region, the Composite Region, and the 

 Leguminous Region respectively. 



That the flora of the Central Region should differ widely from the floras of the 

 Eastern and Western Regions is accounted for by the great elevation above the 

 sea of the central part of the island. But how are we to explain the existence of 

 so great a difference between the floras of the Eastern and Western Regions, 

 occupying, as they do, the same latitudinal and altitudinal positions, for of the 

 1,355 plants found in the Eastern and Western Repfions only 89 are common to 

 both ? The explanation is believed to be simple. The central elevated plateau of 

 the island, which runs from north to south, is undoubtedly of very great antiquity, 

 having existed not improbably from palaeozoic times, and has therefore always 

 formed a barrier between the floras of the Eastern and Western Regions. The 

 floras therefore, even if they were formerly similar, have had abundance of time 

 to become differentiated in character ; and if they were originally different, they 

 have been kept, by the existence of the mountain barrier, distinct to the present 

 day. 



In another paper of a much more extensive character than the present one, 

 the author has entered into detail in regard to the character of the three 

 Regions. He will not, however, go into particulars here. One thing, however 

 may be mentioned of a somewhat interesting character. In the higher portions 

 of the Central Region there are some half-Kiozen plants whose distribution is 

 remarkable. Of these one is a violet, which is also found at the height of 10,000 

 feet in Fernando Po and 7,000 feet in the Cameroons in West Africa, almost under 

 the equator, and also in the mountains of Abyssinia. A geranium has a similar 

 distribution, so have Caucalis melanantha, Drosern rainentacea, and Lonchitis 

 occidentalis, which appear also on the mountains of Angola and Guinea, and 

 Agauvia salicifolia in Reunion, the Cameroons, and the high land about 

 Nyafsa. Sanicula europcsa 'occurs in Central Madagascar, the mountains of 

 Abyssinia, the Cape, 4,000-7,000 feet in the Cameroons, 4,000 feet in Fernando 

 Po, and is widely spread through Europe and other parts of the north temperate 

 zone.' Cyanotis nodiflora finds a home in Angola and Central Madagascar. These 

 facts point plainly to the existence of a former cold (or temperate) climate within 

 the tropics, followed by a warmer period, when these temperate plants, in order 

 to maintain an existence, were compelled to retreat up the mountains, where they 

 remain to the present day. 



In considering the flora of Madagascar as a whole, one of the first things that 

 strikes one is that the island must be of immense antiquity. About four-fifths of 



