440 BOTANICAL GAZETTE [JUNE 
a short distance through soft limestone with regular slopes steeply 
V-shaped, then through sandstone conglomerate, which being 
very friable weathers rapidly. The faces of the sandstone slopes 
show a series of low cliffs (fig. 2) alternating with nearly bare talus. 
The walls of the cafion are exceedingly unstable. 
Ephedra is sparsely distributed along the cafion walls for nearly 
four miles, occurring only on the most exposed and most unstable 
slopes in clumps of from four or five plants to sometimes twenty 
1.—Limestone cliff at entrance to the box cafion of Rifle Creek, near the 
Fic 
upper limit of Ephedra, which is found in small quantities at the top and in the talus 
slope at the base. 
or infrequently more. Isolated plants are rare and an examination 
of one of these showed that it had been torn from a clump on a cliff 
above by a small landslide. The vertical range is as sharply 
limited as is the horizontal, no plants being found at an altitude 
below 2000 nor above 2200 meters. The clusters are most abundant 
on the sandstone slopes, the greatest display and most vigorous 
plants being near the lower limiting altitude (fig. 2); thence 
running up the ridges between the small side cafions and becoming 
