105 



vegetation itself as much as on any fundamental environmental 

 factor.* The contrast between the California and Great Basin 

 "microphyll deserts" (which have very little rain in summer) 

 and the Texas and Arizona "succulent deserts" (which have 

 frequent summer showers) in number of thorny plants might 

 have been brought out, for thorns are abundant in the latter 

 and comparatively scarce in the former. 



"Pacific semi-desert" (which is chiefly confined to California) 

 would doubtless be subdivided if a larger scale were used, for as 

 here mapped it includes such diverse types as the chaparral 

 thickets and live-oak groves of the coast ranges and the grass- 

 land and scattered white oaks in the great central valley. The 

 term "semi-desert" too is about as inappropriate for the cool 

 foggy coast north of Santa Barbara as it is for the hotter and 

 drier but very fertile alluvial Sacramento valley. 



The prairies of Long Island and Florida are justly omitted 

 on account of their small size, but those of eastern Arkansas and 

 the Louisiana-Texas coast region should have been mapped (see 

 maps of those states in the fifth volume of the Tenth Census). 

 The "southeastern evergreen-deciduous transition forest." 

 should have been widened out considerably in both directions, 

 especially in Georgia, and should have been represented also in 

 northern Florida. (See map of Floiida in Geog. Review 2: 362. 

 Nov. 1 916.) The pine-barrens of Long Island and New Jersey 

 differ in many ways from those of the southeastern states, and 

 are also widely separated from them. 



" Northern mesophytic evergreen forest" is a large and hetero- 

 geneous category, extending w^ith some interruptions from Maine 

 to California and New Mexico (and corresponding approximately 

 with Merriam's " boreal zone."t Under this head seem to be 

 included the dense spruce and balsam forests from Maine to Minne- 

 sota, with little or no grass and many berries, subject to fifty 

 inches or more of snow every winter, and destructive fires once 

 or twice in a century; the white pine and hemlock forests of 



* See Pop. Sci. Monthly 85: 338 (footnote). 1914; New Int. Encyc. 22: 

 698-700. 1916; Sci. Monthly 4: 458. 1917. 



fSee map in his "Life zones and crop zones of the United States" (U. S. 

 Biol. Surv. Bull. 10. 1898). 



