ILLUSTRATIONS (13). CINCHONA-BARK HUNTERS. 281 



which I had an opportunity of observing on the declivity of 

 the elevated plains of Bogota and Popayan, and in the neigh- 

 bourhood of Loxa, in descending towards the unhealthy valley 

 of the Catamayo, and to the river Amazon. The febrifuge- 

 bark hunters (Cazadores de Cascarilla), as those Indians and 

 Mestizoes are called at Loxa, who each year collect the most 

 efficacious of all the medicinal barks, the Cinchona Condaminea^ 

 among the lonely mountains of Caxanuma, Uritusinga, and 

 Rumisitana, undergo considerable danger in climbing to the 

 summits of the highest forest-trees, in order to obtain an 

 extended view, from which they may distinguish the scattered, 

 slender, and aspiring trunks of the Cinchona, by the reddish 

 tint of their large leaves. The mean temperature of this 

 important forest region (between 4° and 4^° south lat.) varies 

 from 60 3 to 68° Fahr., at an absolute height of from 6400 to 

 8000 feet above the level of the sea.* 



In considering the distribution of species, we may also, 

 independently of individual multiplication and mass, compare 

 together the absolute number which belong to each family. 

 Such a mode of comparison, which was employed by Decan- 

 dolle,f has been extended by Kunth to more than 3300 of the 

 species of Compositae with which we are at present acquainted. 

 It does not show what family preponderates by individual 

 mass, or by the number of its species, over other phanerogamic 

 forms, but it simply indicates how many of the species of one 

 and the same family are indigenous in any one country or 

 portion of the earth. The results of this method are, on the 

 whole, more exact, because they are obtained by a careful 

 study of the separate families, without requiring that the 

 whole number of the phanerogamia of every country should 

 be known. Thus, for instance, the most varied forms of Ferns 

 are found in the tropical zone, each genus presenting the 

 greatest number of species in the temperate, humid, and 

 shaded mountainous parts of islands. While these species are 

 less numerous in passing from tropical regions to the temperate 

 zone, their absolute number diminishes still more in approach- 

 ing nearer to the poles. Although the frigid zone, as, for 

 instance, Lapland, supports species of the families which are 



* Humboldt et Bonpland, Plantes equinoxiales, t. i. p. 33, tab. 10. 

 f See his -work, Regni Vegetal His Sy sterna naturale, t. i. pp. 128, 

 396, 439, 464, 510. 



