INTaODUCTOEY ESSAY. 113 



time a nearly complete identity of vegetation. Many North 

 African or Arabian forms, such as Peganum Harmala, Fagonia 

 Cretica, Balanites ^gyptiaca, 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, Bal- 

 samodendron, Astragalus hamatus and others, Cucwmis Colo- 

 cynthis, Berthelotia, Anticharis Arabica, spinous Acanthacem, 

 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 : Capparis, Grewia, 

 SterculiacetB, TiliacecB, columnar Euphorbia, and many other 

 Euphorbiacea, Antidesma, Lepidostachys, Olacinea, 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 



* Folanisia, Ch/nandropsis, Urena, Sida, Meloclda, Riedleya, Corchorus, 

 Trmmfetta, ^schij-nomene^ Sniitliiay Indigoferay Dolichos^ Ammannia, Owcwhir 

 tacem, Shmea, Vernonia cinerea, Exacum, SoropTmlariacem, Leucas, Ocymwm, 

 SedycMum, Amommn, G-loriosa, Commelt/naoecB, QrasseB, and Cyperacem. 



t The Melicmthus Himalayamis, described by Planchon, is a garden plant, 

 introduced from the Cape of Grood Hope into the Himalaya, and is not dis- 

 tinct from the common Capo species. 



1 



