i82 GEOLOGICAL SURVEY OF NEW JERSEY. 



Salem, the typical deciduoxis region or zone will be found to lie 

 north of the former and the typical coniferous zone south of the 

 latter, while between the two is an area about sixteen miles 

 wide which may be termed the " tension zone," because it is 

 there that the two floras meet and overlap, producing a constant 

 state of strain or tension in the struggle for advantage. * 



Figure 1. Map showing Forest Zones 



Within the limits of either the deciduous or the coniferous 

 zone the conditions are more or less uniform ; the typical or 

 characteristic species of each have become firmly established in 

 the environment most favorable for them, or unfavorable for 

 others, and the struggle for advantage is largely between indi- 

 viduals of the same species. In the tension zone, however, the 

 struggle is not only between individuals of the same species, but 

 also between different species. The elements in the deciduous 



* An excellent general discussion of floral tensions may be found in Mr. Conway MacMillan's 

 " Metaspermae of the Minnesota Valley," pp. 594-600. Repts. Geol. and Nat. Hist. Surv. Minn., 

 Botanical Series, Vol. I. 1892. 



