260 AGRICULTURAL INDICATORS. 



nants have received little careful study. In spite of these facts, there are 

 certain obvious correlations where varieties differ in some clear-cut quality, 

 such as earliness or dwarfness. Both of these are related to the evasion of 

 drought or frost, and can be correlated in some measure with indicators of 

 changing altitude or latitude, or with decreasing rainfall. It should be borne 

 in mind also that each variety primarily represents a certain degree of adjust- 

 ment to particular conditions, and that some of them are certain to be replaced 

 by other varieties as a result of longer trial or changing demands. 



Wheat exhibits the best indicator correlations with varieties because of its 

 greater differentiation and wider area. Among the durum wheats, Arnautka 

 is indicated as the best variety by the true prairies with greater rainfall and 

 shorter season. Of the spring wheats, Preston is generally indicated by true 

 prairie, Marquis by mixed, and Bart by the bunch-grass prairie. Winter 

 wheats are less clearly indicated owing to their greater drought evasion, but 

 the Turkey and Kharkof are the principal varieties in the true prairies, and 

 various strains of Crimean in the short-grass plains and the sagebrush. The 

 soft winter wheats correspond with the subclimax prairies more or less nearly, 

 while the hard varieties correspond with the true prairies and short-grass plains, 

 which are relatively drier and colder. The varieties of oats show a fair degree 

 of correspondence with the grassland associations. Kherson generally gives 

 the best yields in the true prairie, Burt in the short-grass association, 60-day 

 in the mixed prairie, and 60-day or Kherson in the bunch-grass prairie. In 

 Kansas, Blackhull kafir is the best variety in the subclimax and true prairies, 

 Pink kafir in the broad transition to the short-grass, and Dwarf Blackhull in 

 the short-grass proper, where it enters into competition with Dwarf milo and 

 feterita. Orange sorgo is correlated with the subclimax and true prairies, 

 and Red Amber with the transition and the short-grass plains. 



Life zones and crop zones. — Merriam's classic paper upon the life zones and 

 crop zones of the United States recognized seven divisions, the Arctic-Alpine, 

 Hudsonian, Canadian, Transition, Upper Austral, Lower Austral, and 

 Tropical (1898:18; 1890:18). The most important of these were sub- 

 divided into faunal areas, of which the Arid Transition, Pacific Coast Transi- 

 tion, Upper Sonoran, and Lower Sonoran are the ones found chiefly in the 

 West. Lists of crops and their varieties were given for each of the areas and 

 the zone ranges of crops were indicated by tables. These represented the 

 most important correlations and were undoubtedly of value as a record of the 

 results of experience and experiment up to 1898, though naturally many of 

 the varieties have since been superseded. Many of these correlations were 

 necessarily the same as for indicator communities in the same regions. Since 

 the basis of Merriam's work was floristic and faunistic rather than ecological, 

 the correlations were for the most part more general and less accurate. As 

 has been indicated earlier, this was a necessary outcome of regarding tem- 

 perature and fauna as the primary bases for such correlations rather than 

 water and vegetation. One interesting consequence was the much greater 

 use made of perennial crops, particularly the fruits, since these are naturally 

 more subject to unfavorable temperatures than the annual ones. The need 

 for a finer division of the faunal areas is well illustrated by the Upper Sonoran, 

 which includes the grassland, sagebrush, chaparral, and woodland climaxes. 

 The difficulty of correlating crops with such an extensive and varied area is 

 mentioned by Cary in his discussion of this zone in Colorado (1911: 30): 



