HARSHBERGER: AMERICAN HEATHS AND PINE HEATHS 183 
glacial soils prevent the deciduous trees of large size from spreading 
out of the valleys, where they are protected, and even the pitch-pine, 
recently introduced into Nantucket, follows the valleys and protected 
slopes of the hills. In all probability, when the pine-barren region of 
New Jersey was an island, an oceanic climate prevailed. The typic 
heathland of which the Coremal is a part was left as a relict in the 
plains of New Jersey. The pine forest in those early times probably 
filled the valleys and later spread over the hills until all of the region 
was covered with pine forest except the areas represented by the 
Upper and Lower Plains, where edaphic conditions prevented the 
growth of tall pine trees. The heathland of this early time was 
Fic. 6. Broom-crowberry (Corema Conradii) along cart road, Warren Grove, 
N. J. In flower, April 7, 1917. 5 
finally converted into the present pine-heath. Graebner has detailed 
a similar conversion of heath into pine forest by the invasion of 
pines, and in such German pine forests the undergrowth consists of 
characteristic heath plants, hence the term Kiefern-heide applied to 
this pine forest with an undergrowth of heath plants. 
The pine trees have been unable to grow to tall size in the New 
Jersey Coremal because of a hard layer of soil immediately below the 
upper sandy layer (Fig. 6). This layer corresponds to the caleche of 
Mexico, the plow-sole of agriculturists and the Ortstein of the Germans. 
