(M / THE OAK-VEGETATION OF AMERICA. 
rifolia, and glabrata. "Many of them form only dense thickets, inter- 
woven with numerous Convolvuli, among which is the important medi- - 
einal C. Purga. Climbing woody grasses, species of Panicum, ascend 
the branches. In these forests we now meet with many sorts of trees, 
which remind us of Europe, such as the Hornbeam, Lime, Willow and 
Cornel, mixed with a multitude of noble trees of the Laurel tribe. 
At an elevation of 8 to 10,000 feet the Oak is only found scattered 
singly among the Pines. It has thick woolly leaves, and mostly long 
fruit-stalks, or racemes of fruit. We find here Q. spicata, reticulata, 
chrysophylla, pulchella, and others, The more perfect parasites now 
. almost entirely disappear, only some sorts of Viscum still continuing ; 
but Mosses and Lichens abound on the Oaks. Long beards of Usnea 
barbata hang down from the branches, in the same fashion as Til- 
 landsia usneoides in the hot region. It is only upon the volcano of 
_ Orizaba at an elevation of 12,000 feet that the Oak ceases entirely. 
— Having thus given a sketch of the changes, which the Oak under- 
goes in the various regions, from the torrid coast of Mexico to the 
_ highest points on the eastern Cordilleras, we now proceed to the Oak- 
vegetation in the interior of the country. . 
_ The immense highlands, which occupy the greatest proportion of the 
interior of Mexico, are separated by high Cordilleras from both coasts 
towards the east and west, and are besides subdivided into various large 
and small tracts by chains of mountains; the smaller tracts having the 
appearance of long valleys, the bottom of which nevertheless is ele- 
vated from 5000 to 8000 feet above the sea. The climate is temperate 
and dry; the vegetation scanty, but peculiar. It is only where the 
mountains are so elevated, as to reach beyond the lower cloud-belt, 
that the climate becomes moister and the woody forms more powerful ; 
forests cover their sides, wbile the highlands and the low hills are almost 
devoid of trees, This causes a great obstacle to the establishment 
of industrial and manufacturing pursuits in the interior; which will be 
_ easily understood when it is recollected, that the most populous towns 
in Mexico are situated on its highlands, or in such valleys as are under 
_ the similar conditions with these; that fuel is expensive, on account 
. of the great distance it has to be brought on mules, through the most 
. difficult mountain-paths, and in small loads. It is principally the Oak 
which affords fuel in the interior of Mexico; enormous quantities being 
likewise converted into charcoal. Such has been the destruction of 
