INTRODUCTORY ESSAY. 113 



time a nearly complete identity of vegetation. Many North 

 African or Arabian forms, such as Peganum Harmala, Fagonia 

 Cretica, Balanites JEgyptiaca, Acacia Arabica, Alhagi, Gran- 

 gea, Calotropis, Salvadora Persica, extend throughout all the 

 drier parts of India. Others have a less extensive range, 

 being only found in Northern and Western India : of these, 

 Malcolmia Africana, Farsetia, several species of Cleome, BaU 

 samodendron, Astragalus hamatus and others, Cucumis Colo- 

 cynthis, Berthelotia , Anticharis Arabica, spinous Acanthace<£, 

 Cometes, Forskalea, Populus Euphratica, Ephedra, Salix JE- 

 gyptiaca, Crypsis, etc. etc., may be mentioned as instances. 

 In India, as in Africa, this peculiar vegetation passes by insen- 

 sible gradations into the European Flora on the one hand, 

 and into the tropical on the other. 



7. The Tropical African type. — Though tropical Asia and 

 Africa are separated by a vast expanse of ocean, there is a 

 striking similarity in their vegetation. This is shown not 

 only by the Identity of the annual vegetation which springs 

 up during the rainy season % but by a great similarity in the 

 families and genera of the trees and shrubs s Capparis, Grewia, 

 SterculiacetJBj Tiliacea, columnar Euphorbia, and many other 

 Euphorbiacece, Antidesma, Lepidostachys, Olacinece, Acacia, 

 and Rubiacece, may be mentioned as examples. 



Too little is known of the African Flora to enable any de- 

 finite conclusions to be drawn as to the numerical value of 

 this type in India, but it is evidently an important onef. 



A curious affinity may also be traced between the mountain 

 vegetation of western tropical Africa and that of the Penin- 

 sular chain, where the absence or comparative rarity of many 

 of the principal features of the Malayan Flora has already 



JPolanisia, Chynandropsis, Urena, Sida, MelocAia, Biedleya t Cor chorus , 



Triumfetta, JEschynomene, Smithia, Indigofera, Dolickos, Ammannia, Cucurbi- 



tacece, JBlumea, Vernonia cinerea^ Exaeum, ScropAulariacea, Leucas, Ocytnum, 



Bedychinm, Amomum, Gloriosa, Commelynacea, Grasses, and Cyperacea. 



t The Melianthus Himalayanus, described by Phmchon, is a garden plant, 



introduced from the Cape of Good Hope into the Himalaya, and hi not dis- 



«mni' 



y 



