326 THE OAK-VEGETATION OF AMERICA. 
in this respect corresponding more with the Chinese and Himalayan 
sorts; and finally the before-mentioned Q. Hindsii with eatable fruit. 
= Most of the North-west American and the Californian species descend 
from the mountains into the plains; the evergreen species extend on 
the west coast further into the north, than on the east coast, which is 
caused by the milder climate derived from the warm currents of the 
South Sea. 
Before quitting the temperate North ne we may point out the 
following common characters of its Oaks: deep-lobed leaves predomi- 
nate, giving the trees an habitual likeness with our North European 
sorts ; most species have small oval fruits, and these are generally sessile, 
or very short-peduncled. 
New Mexico and Texas, which have been visited botanically by 
Berlandier, Lindheimer, Fendler, Wright, and Drummond, have a sub- 
tropical climate, and, as regards their Oaks, correspond much with the 
southernmost United States. Thus we meet again here with Q. virens, 
which makes its appearance under an incredible variety of forms; 
Q. cinerea, falcata, lyrata; aquatica, nigra, P'loridana, and Q. Gambellii 
from the mountains in the vicinity of Santa Fé. Most species extend 
as far as the equator. 
= Previous to entering upon our account of the Oak-region of Mexico, 
we have to observe that the entire West Indian Archipelago is destitute 
of Oaks, which is somewhat surprising, since several of the islands have 
a considerable size and rise into respectable mountains, where even the 
fir-tribe makes its appearance. Properties of the soil unfavourable for 
. the production of the Oak, are probably the cause of this, though I 
. know too little of West Indian geognosy, to form any correct opinion 
on this subject. 
Wherever I have met with Oaks on the continent of America, I have 
found them growing in a very heavy clay, deep red from iron, and 
wholly wanting all chalk admixture. In those parts of Cuba which I 
_ visited, I nowhere observed that sort of soil; but the clay was mixed 
with chalk. I am ignorant of the condition, in this respect, of the 
more elevated mountains of Cuba, especially in the eastern part of 
Sierra Maestra, where it might be expected to find Oaks in high situa- 
- tions, but where none are as yet known to exist. 
We now come to the tropical zone of continental America, where 
the genus attains its maximum. The reason why Mexico is so ex- 
