32 DISTRIBUTION OF THE OAK TRIBE. 



probably suffer a not inconsiderable reduction, when the species are critically revised. I venture , 

 nevertheless, to assert, that the American Oaks surpass in number the aggregate amount from all 

 other parts of the world, with reference only to the forms preserved in the herbaria of Europe— nay, 

 to those only which are at present in my hands. 



' It is deserving of notice, that while other parts of the world have several Oak-species in common, 

 the case is not so as regards America, where not one single species exists from thence. The cause 

 of this is to be traced, partly in the circumstance, that neither in America nor Asia do the Oaks 

 extend so far north, as to bo able to migrate from one quarter into another, where the transition is 

 shortest ; and partly in the extraordinarily brief vitality of the acorn, by which the ocean is pre- 

 vented from transporting them in a living condition, from one part of the globe to the other. 



' As in Europe, north of the Alps, the Oaks are deciduous, and continue leafless during all the 

 winter, while in the Mediterranean they are evergreen ; so also do we find, that, in North Amcriea> 

 to the north of the equator, and as far as a considerable difference exists between the temperature 

 of summer and winter, the Oaks arc deciduous ; while those in its tropical and subtropical zone, are 

 evergreen. 



' It has hitherto been a prevailing notion, that the Oak-form is peculiarly characteristic of the 

 temperate zone. But whether we look to the number of species, the beauty of the forms, or the size 

 of particular organs (leaves,'fruits, cups), we shall find their maximum in 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 express reservation, that, ordinarily, the 

 conditions of vegetation arc 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 tropical countries. 



' Moreover, it must not be supposed, that it is in the temperate zone, where the Oak developcs 

 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 

 Mexicau 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 account of its iron-hardness and toughness it is 

 converted into tools, which in other parts are made of metal. 



' It is known that there are Oaks in the south of Europe, Asia Minor, and in northern Africa 

 with edible fruits (Quercus esculenta, Ilex, Ballota) ; 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-Californiau 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 collections 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. 



' A 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 some species, whose leaves become blood-red towards the fall, thereby imparting to the 

 forests in autumn a magnificent appearance ; among these are Q. coccinea and rubra. — From 

 Hooker' 8 Journal of Botany, translated from the Danish of Professor Liebmann. 



