THE OAK-VEGETATION OF AMERICA. 323 
the tropical zone, that is in the Sunda Islands of the Old World, and 
tropical Mexico in the New. It must be admitted however that, in 
the hot zone, it is especially at an elevation above the sea enjoying a 
temperate climate, that the Oak predominates; though with this ex- 
press reservation, that, ordinarily, the conditions of vegetation are far 
more favourable in the temperate mountain region within the tropics, 
than in the temperate zone, which has commonly been placed on a 
parallel with the former; for, neither in the seasons, nor between night 
and day, is the difference so great in the temperate region of the 
tropical zone, as in the temperate zone; and the quantity of rain, that 
important condition of vegetation, is far more considerable within, than 
without the tropics, and increases much at mountain elevations in tro- 
pical countries. 
Moreover, it must not to be supposed, that it is in the temperate 
zone, where the Oak developes itself most favourably, with regard to 
the appliances of its wood for useful purposes; or where its trunk 
attains the greatest size. ‘There are as mighty Oaks in the torrid zone 
with perhaps higher trunks, though scarcely of greater diameter; and 
as regards the hardness of its wood, many of the Mexican species 
greatly exceed those of the temperate zone in that respect, so that the 
wood is hardly to be wrought by means of ordinary tools ; nay, on ac- 
count of its iron-hardness and toughness it is converted into tools, 
which in other parts are made of metal. ar 
It is known that there are Oaks in the south of Europe, Asia Minor, 
and in northern Africa with edible fruits (Quercus esculenta, Ilex, Bal- 
lota); the acorns being sold like our filberts and walnuts. Rich 
as America is in Oaks, not a single esculent species was known until 
within the last few years, Captain Fremont became acquainted with 
such a species among the indigenous Indian tribes of the western slope — 
of the Upper-Californian Cordilleras, who collect the acorns for winter . 
store, and to a great extent are supported by them. The species is 
Quercus Hindsii, described already by Hooker and Arnott in the col- 
lections brought home from Captain Beechey's Expedition ; though the 
use of the fruit as an article of food, was unknown before the journey 
of Fremont. ; í 
À small group of deciduous Oaks, not ripening their fruit until the 
second year, is peculiar to North America. To it belong Q. Phellos, 
Banisteri, rubra, coccinea, tinctoria, palustris, and others. Likewise 
