1920] PALMER, LIGNEOUS FLORA OF THE STAKED PLAINS 101 



suggests many interesting questions. In seeking the answers the origin of 

 the plains topography and especially that of the canyons must be taken into 

 account no less than the present ecological conditions and the possible 



coo 



giving it its present composition. 



All of the phenomena observable in the canyons serve to impress the 

 observer with a realization of how rapidly the work of excavation is going 

 on and how comparatively modern their entire history may be. The re- 

 markable facility with which some of the small streams have been able to 

 cut deeply for many miles back into the plains plateau is attributable not 

 only to the generally soft character of the deposits encountered but also 

 probably to a recent uplift of the region, after the streams had defined their 

 present courses, thus increasing the gradient and augmenting their erosive 

 activities as they approached the escarpment. 



It was the writer's good fortune in one respect, although not conducive 

 to comfort or successful plant collecting at the time, to be in the Paloduro 

 Canyon during a very heavy rainfall. Through the greater part of a day 

 and night the rain came down in torrents, and when it slackened on the 

 following morning the little stream across which I had waded several times 

 on stepping-stones, scarcely wetting my boots, had become a roaring torrent 

 more than a hundred yards across in places; fences and water-gates had 

 been carried away and many of the Cottonwood, Mesquite and other trees 

 along the river margins had been uprooted and borne down stream through 

 the undermining of the banks, which were still crumbling at a rapid rate. 

 On every hand could be heard the crashing and booming of falling earth and 

 rock. When it became possible to approach the walls of the canyon and 

 enter the deep side galleries the destructive effects of the elemental warfare 

 were everywhere' apparent. Great sections of the cap-rock ledges had been 

 undermined and had tumbled down into the stream or were piled up at the 

 base of the clifTs and slides of rock and earth on a large scale were going on 

 in the saturated and fragile beds for some time after the storm. 



The new sections of unoccupied land thus constantly being exposed mvite 

 the settlement of such plant pioneers as can gain a foothold. The compe- 

 tition between these first settlers is usually very slight but not all of them 

 that have the hardihood to attempt colonization on these often dry and 

 sterile lands succeed or prosper. Many tragedies ensue, too, from the un- 

 stable nature of the rapidly changing surface; but gradually those species, 

 amongst the plants available or such as fortuitously enter the area, which 

 are best adapted to all of the conditions encountered establish themselves 



and become dominant. 



In general the protection afforded in the canyons from the almost con- 

 stant force of the dry winds of summer and the cold blasts of winter that 

 prevail upon the open plains, together with the more abundant water sup- 

 ply and the diversity of surface and soil are favorable to the development 

 of a rich and varied flora and make possible there the growth of many plants 

 that cannot survive beyond their limits in the Staked Plains region. There 



