sn 



ZONES AND REGIONS [Pt. Ill, Sect. II 



Lorenzo basin, but elsewhere has merely smaller woods and clumps of it in 

 the midst of other wood. In the latter, Pinus Strobus, like most pines, is 

 associated with very sandy soil. Less permeable areas of soil are occupied 



Fig. 315. Picea nigra, Link (P. rubra, A. Dietr.), in Pennsylvania. From a photograph 



by Rothrock. 



by pure woods of Picea nigra (Fig. 315), or by broad-leaved forests. Tem- 

 perature may possibly be the controlling factor. Elsewhere Picea nigra grows 



