60 THE NATURAL HISTOEY EEVIEW. 



istent Tegetation of the Tropics, obliging us to regard the majority 

 of existing tropical plants as modern creations compared with the 

 temperate. "With ourselves it is a matter of doubt whether the 

 vegetation of the Tropics (exclusive of the temperate regions of its 

 mountains) is richer generically and specifically than that of the 

 Temperate zones. If it should prove to be richer, it presents a grave 

 difficulty in the way of Mr. Darwin's hypothesis, and one which he 

 may perhaps best obviate by showing that, owing to the struggle of 

 life being greater in intertropical regions, and the greater activity 

 of the subsidiary agencies (such as rapid development of vegetable life, 

 insects and the elements that tend to hasten change), there has been 

 a more rapid process of difterentiation and selection. There will still, 

 however, be the difficulty of accounting for the uniform distribution of 

 Genera and Orders over the Tropics of the Old and New World, 

 without any obvious means of transoceanic migration between them. 



The last point to which we shall allude in the West Indian Flora 

 is the astonishing number of Ferns it contains. Dr. Grisebach 

 adopts Sir W. Hooker's moderate estimate of the value of specific 

 characters, and according to it enumerates no less than 340 species (ex- 

 clusive of 23 Lycopodiacece). Considering the area of the two islands 

 which contain almost the whole of them, viz. Jamaica and Trinidad, 

 this number is enormous. Ceylon, a very rich country, contains 

 205 species and 14 Lycopodiacece. Jamaica alone contains 290 Terns 

 and 17 Lycopodiacece. 



In Mr. Thwaites' Enumeratio Plantarum Zeylanise, we have a 

 work whose modest title covers a great amount of most accurate 

 botanical matter, which will prove of the greatest use to the Indian 

 as well as to the Cingalese Botanist. It comprises the Flowering 

 plants and Ferns of .one of the richest tropical islands in the world, 

 perhaps the very richest, considering its area and elevation ; and one 

 which derives an additional interest from being the first the Flora of 

 which was published in a systematic form, and this too by the great 

 Linnseus. 



The number of species described by Linnseus in 1757 as indige- 

 nous to Ceylon was 657. Mr. Thwaites enumerates no less than 2832, 

 which might be considerably enlarged by those who take a narrower 

 view of specific limits than he does. On this subject the author says 

 in his preface, " Care has been taken not to multiply species unne- 

 cessarily, for observation has shown that the amount of variation is 

 often considerable in plants, affecting a large range of station, and 



