244 Observations on Humboldt's Works 



number, then the torrid zone of America must have 23,000, and 

 Jamaica 5,000 known phanerogamous plants. It appears, how- 

 ever, that the author ascribes to South America 460 ferns ; but 

 we do not perceive that he has made any use of this number, and 

 he trusts less to his mode of calculation here than in the other 

 families. That the number of the plants of this family, how- 

 ever, increases towards the equator, the author might easily have 

 inferred from his own data ; for he asserts that among the 1,000 

 ferns, which are known*, 760, that is |, are found within the 

 tropics ; but that of the whole number of phanerogamous plants 

 which are known, more than f are within the tropics, is at 

 variance with his calculation p. xi., according to which at least 

 16,000 out of 38,000 grow without the tropics ; for Jamaica he 

 gives, after Schwartz, 764 phanerogamous plants and 103 ferns, 

 which makes the proportion 1:8. He also says, p. 33, that the 

 numbers of known Filices in Lapland, Germany and Jamaica, 

 stand in the following relation, 19 : 40 : 103, and thence deduces, 

 p. 33 as well as p. xiii., the proportions of this family in the 

 three zones, 1, 2, 5t, much higher than those of the known 

 phanerogamous plants. 



Whilst then the ferns actually appear to have their true climate 

 in tropical regions, (the greatest number being found in the 

 West Indian Islands, the Isles of Bourbon and of France); it 

 is very possible that, if a comparison were made between two 

 countries, one lying near the equator, and the other in the tem- 

 perate zone, the result would be, that the latter would be found 

 to possess a smaller number of ferns than the former. But 

 that the ferns should increase, not only from the temperate zone 

 towards the tropics, but also towards the pole, as the author 

 attempts to shew through a comparison between Germany and 

 Lapland, would doubtless be a very remarkable phsenomenon, 

 for these climates, entirely opposite to each other, would have 

 similar effects on vegetation. But we shall see presently, that 



• In fact, this number is too small, for Willdenow has already 1,000 ; and 

 more lately, particularly by M. M. Brown and Desvaux, many others have 

 been made known. 



t Besides, this calculation cannot be admitted. The numbers should be 

 only 1 : 4 : 4. 



