VEGETATION OF BOX CANON. 1 3 



elsewhere cover the mountain some 2,000 feet higher. On the 

 left side was the usual forest of the pinon zone — the two junipers 

 and the nut-pine, just as we had left them half an hour before 

 on the hills above. But the right side, directly opposite, was 

 like a continuation of the desert. Here, on the talus slopes above 

 our heads, were the mesquite, creosote bush, ocotillo, Dasylirioii, 

 Yucca, Agave and various cacti ; in short, precisely the associa- 

 tion of plants that we had been studying the day before at the 

 foot of the mountain 1,500 feet lower down. Within a stone's 

 throw of each other were these well-marked associations of 

 plants, one recalling the woods of jNIichigan, another a part of 

 the pihon forest of the middle slopes of the New iMexico and 

 Arizona mountains, and the third clothing with characteristic 

 xerophytic forms an arm of the great desert that surrounds their 

 base. 



As we proceeded down the canon the same diiTerence of vege- 

 tation on either side was manifested, pihon and juniper on the 

 left, and members of the sotol association on the right ; and not 

 until we finally reached its mouth below did we see the plants of 

 the desert gaining the ascendancy on all sides. 



These facts, deeply impressed on the memory in the few hours 

 that it took to walk the length of the canon, are, evidently enough, 

 connected with present-day conditions. The right side -iof the 

 caiion, as already stated, is fully exposed, through the greater 

 part of its extent, to the direct rays of the sun. The temperature 

 is necessarily higher, the light more intense, the scanty soil more 

 readily dried out, and the diurnal changes of conditions more 

 extreme than on the opposite side. Bearing striking testimony 

 to the effects of these adverse conditions, the scattering indi- 

 viduals of Pill us cdulis that had gained a foothold there were 

 all dead, killed by the drouth of i903-'o4, and were standing stark 

 and black among the desert plants growing in full vigor around 

 them. On the left bank, although an occasional pihon had died 

 under the stress of " the dry year," it was, on the whole, the best 

 growth that was seen during the day's trip, and the sheltered 

 bottom of the canon, with abundant water and an accumulation 

 of humus, could hardly be improved upon as a home for the 



