TWO MILES UP AND DOWN IN AN ARIZONA DESERT. 55 



made possible by the great variation in climax conditions. The 

 differences in temperature between the altitude of the Colorado 

 River and the rim has already been noted above, and it may be 

 possible that there is also a difference in the actual precipitation 

 as well. AMiether the last is true or not, the variation in tem- 

 perature would bring an unequal total evaporation which is of 

 great importance in determining the desertic character of any 

 place. 



Our stay of only three days was far too short to make possible 

 more than the most superficial study of the plants and of their 

 environment. However, it was very apparent that in the canyon 

 there is a rare opportunity, and one which appears to have re- 

 ceived scant attention, for a close study of the relation of plants 

 to their environment. Xot only does the question of altitude 

 enter, but the effects of exposure, and the substrata of different 

 structure and of varied origin come into great prominence. 

 These various factors are not necessarily confused, but stand out 

 in ckar relief and may be definitely measured and possibly their 

 influence as clearly defined. It is to be hoped that some inter- 

 ested botanist will spend his simimer vacation, and longer, in 

 the region of the Grand Canyon and especially in the canyon 

 itself, for as [Nlerriam has well said, "the Grand Canyon of the 

 Colorado is a world in itself, and a great fund of knowledge is 

 in store for the philosophic biologist whose privilege it is to study 

 exhaustively the problems there presented." 



The semiarid region of the Southwest contains a great number 

 of historic and prehistoric ruins of cliff dwellings, towers, com- 

 munal houses, shrines, and burial mounds, examples of which are 

 found in the Flagstaff district of the San Francisco Mountains. 

 The question of the preservation of this vast treasury of infor- 

 mation relative to our prehistoric tribes has come to be a matter 

 of much concern to the American people, and has received special 

 attention from the Secretary of the Interior. Parts of this region 

 are sufficiently rich in prehistoric interest and scenic beauty to 

 warrant their organization into national parks. 



