124 Journal of T^-avel and Natural History 



to a height of 4000 feet. Other characteristic trees are the palm of 

 the Thebaic! (Cucifera Thebaica), the sycamore {Ficus sycomorus), 

 Tamarix articulata, Balanites segyptiaca, Salvadora persica, Zizyphus 

 spina-christi, Salix aegyptiaca, and many species of Acacia. The 

 herbaceous plants are usually spiny, or fleshy, or covered with a 

 thick down. The following are genera which may be mentioned 

 under this head : — Farsetia, Morettia, Anastatica, Schouwia, Zilla, 

 Cleome, Silene, Polycarp^ea, Astragalus (annual species), Neurada, 

 Aizoon, Fagonia, and Plantago. The Flora of the higher mountains 

 of this district resembles that of the plateau sub-region of the last. 

 If we were to separate the plants of the three great continents 

 of the old world into geographical types of primary value, it is 

 probable that six would be the best number to define for Europe 

 and Africa, as follows : — 



1. Arctic-alpine European type of distribution. 



2. Geraianic or Central European type. 



3. Mediterranean type. 



4. Arabo-Saharan or Desert type. 



5. Tropical African type. 



6. Cape type. 



In which case the second, third, and sixth would include a very 

 much larger number of species than the three others. The cha- 

 racteristic plants of M. Boissier's first region would then belong to 

 our type No. 2, and of his fourth region to our type No. 4 ; and 

 in making divisions of primary value, it would probably be best to 

 unite those of his second and third region with type No. 3. But 

 our remarks have already extended so far that we must not enlarge 

 upon this head. 



As the work is certain for a long time to come to be used as a 

 basis for all statements respecting Oriental plants whicli involve 

 figures, there is a matter which has important bearings in this 

 direction which we must explain. M. Boissier's theory, or what is 

 still more to the point, his practice as regards the limitation of 

 species, is very different to that of the English botanists who write 

 upon other than British plants. Many forms which they would 

 ])ass over unnoticed, or class as varieties, he ranks and duly 

 describes as species. Connect this with what has been said about 

 the characteristics of the third botanical region just described, 

 and it will be seen that is a Flora where the consequences of this 

 dififerencc will affect any question of figures materially. It is 

 ])robnbly ([uite tair to count numbers as between the '' Fhira 



