THE OAK-VEGETATION OF AMERICA. E 
Oak-forests during the last 300 years, on account of the many rich 
silver-mines at St. Louis Potosi, Guanajuato, and Zacateca, that the 
smelting of silver is at the present day attended with enormous ex- 
penses for the purchase and transport of charcoal alone. It may be 
easily conceived, that it has been found necessary to relinquish the 
working of even the richest copper and iron mines on account of their 
disproportionate costs; for charcoal had to be brought eighty leagues - 
on clumsy small carts; which was the case especially in regard to the - 
copper-mines at Mazapil and Saltello. à 
The Oak-vegetation in the northern states of the interior is very 
numerous as regards species; but almost all the trees are low and | 
stunted; often only shrubby; not forming dense forests, but standir 
in small groups on the precipitous sides of mountains. Many species 
have large, coriaceous, often rugose, tomentose leaves, and small fruits. - 
They occur chiefly at elevations from 6000 to 8000 feet, and do not - 
produce the same pleasing impression with the Oaks on the eastern 
Cordilleras; their weak, crooked stem, the few irregularly spreading 
branches, and stiff, lead-grey leaves giving them a sombre appear- 
ance, still further augmented by the loads of pendulous ash-grey - 
Tillandsia usneoides, which often cover the Oaks entirely. To give 
some idea of the extent of species found on those arid mountains 
in the interior of Mexico, I will mention the following from the 
silver district Real del Monte: Q. crassipes, Mexicana, lanceolata, lau- 
rina, tridens, depressa, ambigua, glaucescens, chrysophylla, pandurata, 
rugulosa, Grahami, glabrescens, repanda, barbinervis, crassifolia, oneri 
callosa, nitens, reticulata, confertifolia, sideroxyla, ete. 
These species are agaiu found on all the mountains of the intero 
Mexico, from Zacateca to Oajaca. In the silver district of the east 
mountains of the State of Oajaca, I have met with nearly all the spé 
cies which I first knew only from Real del Monte. ; 
It is notorious that the ancient, original seat of the coch 
culture, was on the mountains of Oajaca. The climate on the. 
mountains of $000 to 9000 feet is rough and unsteady, and therefore 
unfavourable for the delicate cochineal insect; nevertheless its culture 
succeeds among the Indians, though with great difficulty ; each sepa- 
rate little insect having to be protected on the flat branches of the Op: 
lia, by means of sheds made by attaching the stiff Oak-leaves to thes 
for which purpose Q. eesssjfolío ia used. Tta tender leaves look like 
