92 BOOKS AND CURRENT LITERATURE 



west have been unable to displace the relatively primitive type found 

 here is thought by Harshberger, on the basis of his studies of the soils 

 of the region (chapter 4) and of the distribution of the subterranean or- 

 gans of pine-barren plants (chapters 16 and 17), to be due largely to the 

 fact that the dominant plants are superfically rooted perennials, whose 

 roots and root-stocks are so intricately matted and interlaced, and whose 

 reciprocal relations are so intimate that "no alien plant has a chance of 

 establishing itself in an area where the original vegetal covering has 

 remained unbroken." 



Nine types of natural plant formations (sic) are distinguished: the 

 pine-barren, cedar swamp, deciduous swamp, savanna, marsh, pond, 

 river bank, bog, and plains formations. In addition to these there are 

 four successional plant formations (sic) : the cranberry bog., scrub oak, 

 oak coppice, and mixed pine-oak formations. These latter arise second- 

 arily, due to the disturbing of the primary associations. The natural 

 formations are discussed in detail, but only the more prominent of 

 these need be mentioned further here. The Pine-Barren Formation, 

 which occupies most of the territory outside of the swamps, comprises 

 a fairly open stand of (mainly) Pinus rigida, associated with which, 

 and forming five or six more or less definite strata of vegetation, are 

 various smaller trees, especially Quercus marilandica and other species 

 of oak, shrubs and herbs. Three distinct facies of the pine-barren for- 

 mation are distinguished: high pine-barren, flat pine-barren and low or 

 wet pine-barren, all of which are treated in some detail. The Plains 

 Formation occupies an elevated tract of country about twenty-five 

 square miles in area, its vegetation consisting of a scrubby forest of 

 Pinus rigida and Quercus marilandica only a few feet high. Because 

 of the abundance here of Corema Conradii, elsewhere absent, this for- 

 mation is designated the Coremal. The causes of the development of 

 this peculiar type of forest have been variously explained. Harsh- 

 berger advances the view, based on an extensive series of cultural experi- 

 ments with the soils of the area, that the character of the vegetation is 

 in large part correlated with the presence of a stiff, impervious subsoil 

 or hard-pan, similar to the Ortstein of the Germans. In connection 

 with the description of the pine-barren and plains vegetation, attention 

 is called to parallel formations in Long Island, Nantucket, and Ger- 

 many. The Savanna Formation presents one of the most unique types 

 of the region. It embraces flat, grassy tracts which occupy low stream 

 terraces and may be miles in extent. In wet savannas, which are more 

 or less arbitrarily separated from swamps, the dominant vegetation 



