260 Dr. J. D. Hooker on the Vegetation 



Hence it appears that James Island is the most rich in species, as might be 

 expected from its central position in the archipelago, and from its containing 

 very elevated land. Albemarle, though the largest, is on the other hand sin- 

 gularly deficient in individuals and kinds, and, as well as Chatham Island, is 

 described as peculiarly sterile and arid. Charles Island, the smallest of all, 

 is almost the richest in species ; and though it does not follow that it is hence 

 peculiarly productive for man, we cannot but couple its varied flora with the 

 fact, that it is the only one hitherto colonized. 



With regard to the relative amount of peculiar species possessed by each 

 islet, it would seem to be affected by its climate, and may be thus expressed : 



Charles Island has 22 species common to other islets, which are as 1 : 4'4 of its whole flora. 

 James Island has 23 species common to other islets, which are as 1 : 4"3 of its whole flora. 

 Albemarle Island has 18 species common to other islets, which are as 1 : 2' 6 of its whole flora. 

 Chatham Island has 17 species common to other islets, which are as 1 : 2'4 of its whole flora. 



This accordance of the proportions obtained for the two fertile islets and of 

 those for the two sterile is very striking, and especially as they are obtained 

 from collections made by six different and wholly independent voyagers, and 

 indicate that sterility of soil has proved an important agent in preventing the 

 confusion of the floras, and also shows how few are the agents of migration ; 

 for Albemarle being the westernmost, and Chatham the easternmost of the 

 whole archipelago, they would otherwise have shown very different propor- 

 tions. 



If we analyse the florulse still further, and seek to know how far each has 

 profited by immigrants from America, a similar difference will be found be- 

 tween the fertile and the sterile islets. 



Charles Island contains 49 American plants, which are to whole flora as 1 : V9. 



James Island contains 52 American plants, which are to whole flora as 1 : 1'9. 



Albemarle Island contains 20 American plants, which are to whole flora as 1 : 2-3. 



Chatham Island contains 19 American plants, which are to whole flora as 1 : 2-1. 



Whence it appears that the fertile islets, though in position not more favour- 

 ably placed for receiving the plants of the American coast, still show, not only 

 numerically but proportionally, their aptitude for supporting a richer flora 

 than that which is peculiar to the group. 

 The nature of the collections is hardly such as to warrant the drawing any 



