296 PHYSIOGNOMY OP PLANTS. 



earth. If the attention of the travelling botanist is engaged by the 

 frequent repetition of the same species, their mass, and the uni- 

 formity of vegetation thus produced, it is even more arrested by the 

 rarity or infrequency of several other species which are valuable to 

 mankind. In tropical regions, where the Rubiacese, Myrtaceae, 

 Leguminosse, or Terebinthaceae, form forests, one is astonished to 

 find the trees of Cinchona, particular species of Swietenia (Maho- 

 gany), Haematoxylon, Styrax, and balsamic Myroxylum, so sparingly 

 distributed. We had occasion, on the declivities of the high plains 

 of Bogota and Popayan, and in the country round Loxa, in descend- 

 ing towards the unhealthy valley of the Catamayo and to the Ama- 

 zons River, to remark the manner in which the trees which furnish 

 the precious fever-bark (species of Cinchona) are found singly and 

 at considerable distances from each other. The China Hunters, 

 Cazadores de Cascarilla (the name given at Loxa to the Indians and 

 Mestizoes who collect each year the most efficacious of all fever- 

 barks, that of the Cinchona Condaminea, among the lonely moun- 

 tains of Caxanuma, TJritusinga, and Rumisitana), climb, not without 

 peril, to the summits of the loftiest forest trees in order to gain a 

 wide prospect, and to discern the solitarily scattered slender aspiring 

 trunks of the trees of which they are in search, and which they 

 recognize by the shining reddish tint of their large leaves. The 

 mean temperature of this important forest region, situated in 4 to 

 4 S. lat. and at an elevation of about 6400 to 8000 English feet, 

 is from 12 to 16 Reaumur (60 a -2 to 68 Fahr.). (Humboldt 

 and Bonpland, Plantes e*quinoxiales, t. i. p. 33, tab. 10.) 



In considering the distribution of species, we may also proceed, 

 without regard to the multiplication of individuals, to the masses 

 which they form or the space which they occupy, and may simply 

 compare together the absolute number of species belonging to a 

 particular family in each country. This is the mode of comparison 

 which Decandolle has employed in the work entitled Regni vegeta- 

 bilis Systema naturale (t i. pp. 128, 396, 439, 464, and 510), and 

 Kunth has carried it out in regard to the whole number of species 

 of Compositse, at present known (above 3300). It does not show 

 which is the predominant family either in the number of species or 

 in the quantity of individuals as compared with other families ; it 



