14 THE PLANT WORLD. 



mesophytic forest that was growing there. The fitting of or- 

 ganism and environment, manifested in the correlation of asso- 

 ciation and habitat, is here perhaps as perfectly realized as one 

 is likely to find it anywhere in this great semi-arid territory, 

 where the perfection of adaptation almost ceases, from constant 



Fig. 5. " On the left was the forest of the pinon zone." 



repetition, to be a wonder. One could hardly wish for a more 

 definite ensemble of conditions than those that are here so mani- 

 festly holding the balance of power and maintaining within a 

 few rods of each other three such widely dift'erent plant asso- 

 ciations. 



But however striking may be the correlation of present envi- 

 ronment and vegetation, it is certain that existing conditions.. 



