18 PREFACE. 



descends below the freezing point, but the island is exposed to frequent 

 and violent winds. 



The numbers in the following Table are taken, for Aden, from Dr. T. 

 Anderson's ' Florula Adenensis ' ( Journ. Linn. Soc. Lond. vol. v. Suppl.), 

 a work drawn up on the same standard as to the limits of genera and 

 species as the Hongkong Plora ; and for Ischia, from Prof. Gussone's 

 ' Enuraeratio Plantarum Vascularium in Insula Inarime provenientium ' 

 (Neapoli, 1854)'. From the latter however I have found it necessary, 

 in order to establish a fair comparison, to deduct the cultivated species, 

 and to reduce the remainder to the specific and generic standard of our 

 Hongkong Flora. 



The Orders most numerous in species 

 GratninesB ... 86 species 



6 Orders have 8 species each. 



5 „ 7 „ 



6 „ 5 ,. 



8 Orders have 4 species each. 

 15 „ 3 



13 » 2 



36 „ 1 



* The discrepancies between the total number of Orders and genera in this and the ■pre- 

 ceding Tables ,s owing to the half-naturalized species being here leckoued, but necessiily 

 excluded when considering geographical areas. >-o»i=<-"/ 



