PHILOSOPHICAL SOCIETY OF WASHINGTON. 105 



tation. It is, however, not the number of species, but individuals 

 which give any particular flora its distinguishing characteristics 

 to all but systematic botanists, and it is upon this, that in the main 

 depends the commercial and industrial value of the plant-life of 

 every region of the globe. It is often the omnipresence of a few, 

 or even of a single, abundant species that stamps its peculiar char- 

 acter upon the landscape of a locality. This is to a far greater 

 extent true of many other regions, especially in the far West, than 

 it is of this ; the vegetation of the rural surroundings of Wash- 

 ington is of a highly varied character, as much so perhaps as that 

 of any part of the United States. And yet there are comparatively 

 few species, which from their abundance chiefly lend character to 

 the landscape, and really constitute the great bulk of the vegeta- 

 tion. The most prominent, if not actually the most numerous of 

 these, are of course, certain trees and notably several species of 

 oak. Probably the most abundant tree here, as in nearly all 

 parts of the country, is Quercus alba, the white oak; but 

 Q. prunus, the chestnut oak, Q. coccinea, the scarlet oak, Q. palus- 

 tris, the swamp oak, and Q. falcata, the Spanish oak, are exceed- 

 ingly common. The most abundant hickory is Carya tomentosa, 

 the mockernut. Liriodendron tidipifera, the tulip-tree, often im- 

 properly called white poplar, besides being one of the commonest 

 trees, is the true monarch of our forests, often attaining immense 

 size. It is a truly beautiful tree whose ample foliage well war- 

 rants the recent apparently successful experiments in introducing 

 it as a shade tree for the streets of the city. Among other common 

 trees may be mentioned the chestnut, ( Castanea vulgaris, Lam, var- 

 Americana, A. D. C, the beech, (Fagus ferruginea,) the red maple, 

 (Acer rubrum,) the sycamore, (Platanus occidentalism the red or river 

 birch, (Betula nigra,) the white elm, (Ulnnts Americana,) the sour 

 gum, (Nyssa multiflora,) the sweet gum, (Liquid-amber Styraciflua,) 

 the scrub pine, (Pinus inops,) the pitch pine, (P. rigida,) and the 

 yellow pine, (P. mitis.) 



Of the smaller trees, Cornus florida, the flowering dogwood and 

 Cercis Canadensis, the red-bud or Judas tree are very abundant, 

 and chiefly conspicuous in the spring from the profusion of their 

 showy blossoms ; all three species of sumac are common. Ham- 

 amelis Virginica, the witch-hazel, and Virburnum prunifolium the 

 black haw abound ; Sassafras officinale, sassafras, Castania pumila, 



