1920] PALMER, LIGNEOUS FLORA OF THE STAKED PLAINS 05 



courses; but as they approach the marginal rim the grade becomes suddenly 

 accelerated; cascades or rapids are formed as they plunge over the precipi- 

 tous cap-rock or rush down the steep slopes of the escarpment. While the 

 streams in this stage are intermittent and their work continues for only a 

 short time after rainy periods they are at such times very active and the na- 

 ture of the deposits they encounter is generally quite favorable for rapid ex- 

 cavation. After the hard stratum of cap-rock has been broken down, which 

 is accomplished rapidly along the overhanging ledges, the soft under-lying 

 strata are easily removed. When the level of ground water is reached, which 

 in the high plains is often several hundred feet below the surface, springs 

 begin to issue along the canyon walls and the streams become perennial. 



The small streams forming the headwaters of Red River have worked out 

 deep channels for many miles back into the interior of the plateau, 

 Paloduro Canyon in Randall and Armstrong Counties, the largest of these, 

 is one of the most remarkable erosion features of the plains and of the entire 

 Southwest. Beginning as several narrow, shallow ravines near Canyon 

 City it rapidly deepens and widens until in some places its floor is from 800 

 to 1000 feet below the level of the plains and more than ten miles in width. 

 This enormous amount of excavation has been accomplished by a small 

 stream in comparatively recent geological times and the work of deepening 



The 



and widening it is going on with undiminished force and rapidity at present. 

 During the summer of 1918 several days were spent by me in exploring this 

 canyon and in studying and making collections of the plants found in it and 

 upon the surrounding plains. As the ecological conditions and flora are 

 quite characteristic of this interesting phase of the Staked Plains the follow- 

 ing notes on the trees and shrubs found in this canyon may be regarded as 



of general application. 



Approaching the canyon in its deeper sections across the plains is an in- 

 teresting experience. Before you lies the seemingly endless prairie, almost 

 as level as a billiard table; in the distance, perhaps, you see a ranch house 

 with its outbuildings and windmills; not a ripple marks the surface of the 

 plain and there is no apparent obstacle to prevent you continuing In a direct 

 course to the settlement. Suddenly you come upon a shallow ravine eating 

 its way into the plain; some low Juniper or Mountain Mahogany bushes 

 appear along an eroded slope for a few yards and then all at once you stand 

 upon the brink of a precipice and at your feet lies a chasm some miles in 

 width and several hundred feet deep. On the opposite side you make out 

 the horizontal line of the plain which continues thence as if unconscious of 

 the interruption. Far down below, the course of a tiny stream meandering 

 through the broad valley is marked by a fringe of trees. The canyon walls 

 are nowhere perpendicular for their entire height, as in some of the western 

 canyons carved through harder strata, but fall away by a series of terraces, 

 slopes and ledges, sometimes with outstanding pinnacles and masses carved 

 into irregular and fantastic forms. There are numerous short but deep side 

 canyons and ravines, which in many places aflPord the only avenues of de- 

 scent into the main canyon. 



