PREFACE. 



17* 



7. The Tempebate Asiatic Tioea. South Siberian, Daburian, 

 Mantcburian, and Japanese plants, wbich attain tbeir southern limit in 

 Hongkong. 



The number of Hongkong species which I -would attribute to each of 

 these Moras is given in the following Table. It must be remembered, 

 however, that these are approximative only, the limits of the areas of 

 species are so vague, their extent so diversified, scarcely two species 

 being ever precisely similar in this respect, that it would be impossible 

 to class them vrith precision, even were their area always perfectly well 

 known to us. 



Table of the Songhong Species, classed according to their Qeographical 



Areas. 



Let these be compared with the Floras of two districts similarly cir- 

 cumstanced as to maritime position and proximity to the mainland, 

 nearly the same in size and elevation above the sea, but widely different 

 as to soil and climate, viz. : — 



1. Aden Peninsula, off the coast of Arabia, in lat. 12° 47'. A dry, 

 parched, volcanic, rocky peninsula or almost an island, about 5 miles 

 long by 3 in breadth, the highest peak attaining 1775 ft., and connected 

 with the mainland by a narrow sandy isthmus. It is exposed through- 

 out the year to a scorching sun, occasionally deprived of rain for a year 

 and a half, and never receives an annual fall of above .6 or 7 inches. 

 Winds are not frequent and seldom violent. 



2. Ischia Island, off the Neapolitan coast, in lat. 40° 41'. A volcanic 

 rocky mountain mass, nearly 6 miles long by 3i in breadth, the highest 

 peak attaining 2,407 ft., and about 9 miles distant from the mainland. 

 Hot and dry during the summer months, it is however well refreshed 

 by rains during the remainder of the year. The thermometer very rarely 



