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 

 w^as 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 



Fig. 6. Broom-crowberry {Corema Conradii) along cart road, Warren Grove, 

 N. J. In flower, April 7, 191 7. 



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. 



