FLORA OF MEXICO. 



55 



essences. Hio-her up follow those glorious woodlands where tlie European and 

 tropical floras are everywhere intermingled ; here flourish the cofl'ee shrub, the 

 banana, the orange, and especially maize and beans, which supply the staple diet of 

 the inhabitants. Then comes the cold region, yielding wheat ; a cereal, however, 

 which is here of far less economic value than maize. 



On the plateaux the prevailing trees are the oak and pine, the former between 

 the altitudes of 5,000 and 8,500 feet, the latter rising from 8,000 to above 13,000 feet. 

 On most of the higher crests the conifers reach or even exceed the altitude of 

 13,500 feet. They are the last arborescent trees that grow on the flanks of the 

 mountains, the space between them and the lower limit of i^erpetual snow being 



Fig. 26. — ^Vegetable Zones in Mexico. 

 Scale 1 : 30,000,000.. 



Alpine Flora. Pinus ponderosa Prairie Flora. Sequoia, 



and edulis. 



Algarrobia 

 glandulosa. 



Finns 

 Aus'ialis. 



Quercus cras^ifolia HjematoxyloTi 

 and reticulata. campechiunum. 



Cereus 

 giganteue. 



Deserts. 



620 Miles. 



exclusively occupied by short herbage and grasses. But owing to the overlapping 

 of the vegetable zones of different temperatures, the pines of the uplands have 

 almost everj^where encroached upon the temperate regions, and have even descended 

 bdow the line of 3,500 feet. 



The dominant types of trees are represented by a great number of species, about 

 seventy-five varieties of the oak having been found on the slopes of Orizaba alone- 

 The ahuehuetcs or " cypresses " of Chapultepec, Atlisco, Oaxaca, which belong to 

 the same species as those of Louisiana {taxodium dktichiDn), grow to a colossul size ; 

 they are classed by Humboldt with the giants of the vegetable kingdom. 



