THE AMERICAN BOTANIST 5 



sues the dry period during which the plants sink into a sort 

 of aestivation and the vegetated areas assume a characteristic 

 gray-green hue. In late July the rains begin again and a sec- 

 ond spring soon sets in with a profusion of flowers scarcely 

 second to that of the earlier season. A number of plants bloom 

 only once, but others bloom twice a year and at the time of my 

 visit were found with both flowers and mature fruits. 



A collector in the desert, especially if it be as remote from 

 civilization as this one, cannot fail to have a variety of inter- 

 esting experiences. He soon discovers, for one thing, that al- 

 though the air is very drv it does not follow that the drying 

 of plants will be an easy matter. Water plants, to be sure, are 

 ready to remove from the driers at the end of twenty-four 

 hours, but the true desert plants have profited by their long ex- 

 perience with a scanty rainfall and hold on to their moisture 

 with a baffling persistence. It required nearly a month to in- 

 duce some to even approach dessication. 



In this region the character of the plant population de- 

 pends in large measure on the character of the soil. In gene- 

 ral, sandy or adobe soils tend to have a more luxuriant flora 

 than do stony areas. For much of the distance between Flag- 

 staff and Tuba, especially in the vicinity of the Little Colorado 

 river, the region is absolutely bare of vegetation. When plant 

 growth of any kind is possible, an eriogohum ( B. divaricatuni) 

 and two saltbushes {Atriplcx saccharin and A. Jonesii) are 

 scattered over the hot soil. The eriogonum appears to be the 

 very last thing to give up the struggle with heat and drouth. 

 One of the surprises of this section is to find a yellow-flowered 

 milkweed, (Asclepias ohtusa) growing singly in situations 

 where the temperature must daily reach 150° F. or more. 



In less inhospitable situations, the ordinary inhabitants of 

 the desert push in, but seldom in numbers large enough to en- 

 tirely cover the soil. Even the most fertile spots have a tuf- 



