148 AN ANALYSIS OF THE FLORA OF SINAL 



sets of examples might be easily increased. They seem to be the out- 

 come of extreme heat and dryness ; the latter reduces the tissues and 

 develops spines, and appears also to be favourable to the growth of pubes- 

 cence in plants. Heat promotes the growth of glandular and odoriferous 

 essences, which a dry atmosphere will intensify ; while, no doubt, many 

 of these modifications are developed, or at least intensified in accordance 

 with the requirements of the species for purposes of protection from 

 enemies, or perpetuation of kind. 



This flora, with these strongly-marked features, extends without 

 interruption from the Cape de Verde Islands and Senegal, across the 

 African and Libyan deserts to Egypt and Nubia, thence across Arabia, 

 the southern part of Mesopotamia and Southern Persia, throughout 

 Beloochistan, South Afghanistan, Scinde, and into the Punjaub, It thus 

 ranges along a belt of surface upwards of 5,000 miles in length from 

 east to west, thinning out at the eastern and western extremities, and 

 widest in the African Desert, where it extends over the space between 

 the tenth and thirty-seventh parallels of latitude. Continuity of repre- 

 sentative or identical flowering plants for so wide a range is without a 

 parallel elsewhere on the earth's surface. The nearest approach to a 

 parallel lies in the circumpolar regions. In many cases the species is 

 identical throughout ; in others closely allied forms represent one another 

 in different countries along the belt. A few conspicuous plants may be 

 mentioned, which extend from the Cape de Verdes and Canaries to India : 

 Citrullus colocynthis, Aizoon canariense, Francoeuria crispa, Picridium 

 tingitanum, Trichodesma africanum, Suseda vermiculata, ^rua javanica, 

 Euphorbia granulata, Andropogon foveolatus and Aristida caerulescens. 

 This flora occupies, in fact, most of the area which was in Tertiary times 

 a sea-bottom extending from the Bay of Bengal to the Atlantic.^ 



On looking to the second column, where these widespread Desert 

 species are thrown together, an illustration of the central position of Sinai 

 with regard to this flora ranging so far east and west will be found. 

 There are 177 Desert species, with a wide range east, west, or south, or 

 in any two, or in all of these directions. Of these, 1 1 2 extend far east- 

 wards, 105 extend far westwards, and sixty have both directions ; so that 



1 See 'Wallace's ' Geog. Dist.,' i., p. 286. 



