280 
west of Garden City and Hempstead, the original prairie vege- 
tation has been almost totally obliterated; but a little south of 
Hicksville there are still a few places where one could describe 
a circle a mile in diameter without including a tree or a house or a 
field. Probably about one fifth of the original prairie area is 
still in its natural condition, except for being intersected by roads. 
Fic. 3. Looking westward in dry valley about a mile south of Westbury Sta- 
tion. Eupatorium hyssopifolium in foreground. Aug. 14, 1909. 
The surface of the Hempstead Plains, like the rest of the 
southern or unglaciated portion of Long Island, is for the most 
part very flat, and slopes gently southward at the rate of about 
one foot in 300. It ranges in altitude from about 60 to 200 feet 
above sea-level. Traversing the plain in a general north and 
south direction are a number of nearly straight broad shallow 
valleys, ten to twenty feet in depth, which are believed by 
geologists to have been formed by glacial streams and not by 
recent erosion. Within the limits of the prairie most of these 
valleys are now dry at all seasons, but farther south some of 
them contain permanent streams. 
The upland vegetation of the Plains comprises about four 
species of trees, a dozen shrubs, sixty herbs, and a few mosses, 
lichens and fungi. The commonest tree is Betula populifolia, 
which in this region is oftener a shrub than a tree, and the other 
trees are Quercus marylandica, Q. stellata, and Pinus rigida, 
