96 JOURNAL OF THE ARNOLD ARBORETUM [vol. ti 



Near the summit of the canyon walls there is a stratum of soft but com- 

 paratively durable limestone several feet in thickness, locally known as the 

 "upper cap-rock." Above it there is sometimes a slope of gravel or cal- 

 careous sand a few feet in thickness; below there Is another slope of only 

 partially consolidated calcareous material, sometimes as much as fifty feet 

 in thickness, resting upon a thick bed of sandstone of Triassic age. This 

 latter formation, called the "lower cap-rock," varies greatly in character. 

 In places it is from 50 to 120 feet in thickness and ranges from a sandy shale 

 to a coarse grained sandstone or conglomerate. Below it are the " red beds " 

 of the Permian, consisting of soft, friable sandstones, clay and gypsum. 

 The brick-red color of these deposits, due to the iron oxide which they con- 

 tain, is imparted to the waters of the stream and gives name and character 

 to the Red River. These soft Permian strata yield readily to erosion and 

 every rain carries away great quantities of material broken down by each 

 rill and temporary torrent. Sections of the cap-rock are constantly being 

 undermined through removal of the softer underlying deposits and huge 

 masses of it frequently piled up at the base of the cliff or in tlie narrow side 

 canyons. Balancing and "toadstool" rocks are frequent where detached 

 masses of the sandstone surmount columns of the softer material. In such 

 places the scenery of the canyon has quite the aspect of the "bad lands" 

 of the Northwest, and amongst the innumerable hillocks and defiles of the 

 more rugged parts it is hard to realize that one is in the midst of the plains 

 and not in a mountainous country. 



Below the level of the plains four principal zones of plant life may be 

 recognized in the canyon. These are the calcareous beds above and below 

 the upper cap-rock, including that stratum, the sandstone section of the 

 lower cap-rock and the broken belt of the Permian deposits below it, the 

 open, comparatively level floor of the main canyon, and the immediate bor- 

 ders of the river and perennial, spring-fed streams. For convenience these 

 may be designated the Upper Cap-rock, Lower Cap-rock and Talus, Can- 

 yon-floor and River-bank zones. 



The following woody plants were collected in Paloduro Canyon at several 

 points in Randall and Armstrong Counties, Texas, but principally at the 

 J. B. Gamble ranch south of Claude in the latter County, and the brief notes 

 are based on observations made during a rather hasty visit: 

 Juniperus vionospenna (Engelm.) Sarg. 



This species, lorally called White Cedar, is one of the most conspicuous if 

 not the most abundant of the woody plants. It occurs from the Upper Cap- 

 rock zone, where it is usually low and shrubby, through the LoM'er Cap- 

 rock-talus zone into the deep protected side canyons. In the last named 

 situations and Mow high protecting bluffs it sometimes becomes a tree 20 

 metres or more high and with a trunk diameter of 5 or 6 decimetres. 

 Juniperus Pinchotii Sudw. 



The species was originally described from this locality and I am applying 

 the name to the tree or shrub called Red Cedar in the canyons, with erect 

 rigid branches and large copper-colored fruit. It is commonly not more 



