8 THE AMERICAN NATURALIST.  [VOL. XXXIII: 
noted Quercus rubra, Hicoria alba, Ulmus Americana, Populus 
tremuloides, Castanea dentata, Liquidambar styraciflua, Betula 
nigra, etc.; and these prevail until the marl area is crossed, and 
the sands and gravels are again encountered, when the condi- 
tions are reversed, pines once more become predominant; and 
this condition prevails until the main marl belt is reached near 
Eatontown, where deciduous trees again replace the pines. The 
lines of demarcation in crossing from one geological formation 
to the other are so sharply defined by the vegetation as to be 
apparent within a fraction of a mile. 
If the same marl area be crossed in a direction at right 
angles to the previously described route, beginning in the 
deciduous zone near Monmouth Junction, an equally significant 
series of facts may be noted. In this vicinity the trees are 
almost wholly deciduous, consisting largely of Quercus rubra, 
Q. alba, Q. velutina, Hicoria alba, H. glabra, H. ovata, Ulmus 
Americana, Fraxinus Americana, Fagus atropunicea, Castanea 
dentata, Liriodendron tulipifera, Liquidambar styraciflua, Pop- 
ulus tremuloides, Carpinus Caroliniana, Platanus occidentalis, 
Acer rubrum, Cornus florida, etc., with occasional groups or 
individuals of Juniperus Virginiana and Pinus Strobus, all of 
large size or young vigorous growth. 
In crossing the clay belt, towards Jamesburg, the first thing 
which attracts attention is that several of these species become 
less prominent, or disappear entirely, and that those which 
continue are noticeably smaller in size and less vigorous in 
growth. Several new species make their appearance, such as 
Quercus ilicifolia, Q. nigra, Pinus Virginiana, etc.; and these 
conditions prevail until well within the borders of the marl belt 
near Englishtown, when the trees again become somewhat 
larger in size. This variation in the size of the trees was 
found to be coincident in most cases with the presence or 
absence of local areas of sand and gravel—the smaller trees 
occurring in connection with these areas, which areas were also 
coincident with the distribution of certain species. For example, 
in one locality, about a mile north of Englishtown, the road 
passes through quite a deep cut, in a sand hill of considerable 
o Ste — and m On this hill is quite a growth : 
