GEOGRAPHICAL SITUATION. 
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humble plants, here spread into lofty trees, many of which are 
adorned by large and beautiful flowers. The richest fruits and 
spices, and the most valuable medicinal plants are found here. 
In ascending the mountains of the torrid zone, as the tempera- 
ture varies, each section has its own distinct plants, and we find 
in succession, the production of every region from the equator to 
the poles.* 
As the mountains of the torrid zone afford every variety of 
climate between their base and their summit, so they are capa- 
ble of producing all the vegetables of every climate ; but as the 
temperature diminishes, as the latitude increases, so, generally 
speaking, the productions, as we proceed from the tropic north- 
ward or southward, correspond with tbs elevation at which the 
same plants will grow upon a mountain within the tropics. 
Every plant requires other circumstances alike ; the same mean 
annual temperature, f for example. The magnificent plantain 
tree and valuable sugar cane require a mean annual heat of 82 
to 73 degrees, but 73 degrees of mean annual heat, is not found 
beyond the 27th degree of latitude ; consequently, the plantain 
and sugar cane will not ripen in the open air in a higher lati- 
tude ; and this Baron Humboldt has found to correspond with 
the height of 3000 feet under the equator ; the cotton plant will 
not flourish without 08 degrees of heat, which is- not found be- 
yond 34 degrees of latitude, which corresponds with about 3,000 
feet of elevation at the equator. The same reasoning applies 
to all other plants, with the' exceptions arising from warm val- 
lies, moisture of air, and richness of soil. 
SEE PLATE I. 
Feel. 
The highest spot on which man ever trod, 19,400 
The highest limit of the lichen plant, 18, 225 
The lowest limit of perpetual snow under the equator, 15,130 
The highest limit of pines under the equator, 12,801 
The highest limit of trees under the equator, 11,125 
The highest limit of oaks under the equator, 10,500 
The highest limit of the Peruvian bark tree, 9,500 
The lowest limit of pines under the equator, 5,685 
The highest limit of palms and bananas, 3,280 
* See plate 1. 
t For explanation of mean annual temperature, see note under vines, 
Lecture 22. 
Production of every region found in ascending mountains of the torrid 
zone — Elevation produces similar effects on vegetation, as distance from 
the equator. 
23 * 
