238 The Plant World. 



aspect is si:nil.ir U) that <>f a mf)re open, easternly one a few 

 hundred feet fa -ther down. An open forest of the Arizona pine 

 is imdergrown \vith whiteleaf oak {Ouercus hypoleuca), a tall, 

 viv^orous shrub, and someti'Ties a shapelv tree as high as fifty 

 feet. A few netleaf oaks (Q. reticulata) and manzanita {Arc- 

 tostaphylos pungens) are ]:)resent, and a rather large number of 

 madrone {Arbutus arizonica) are conspicuous as tall shrubs or 

 gnarled trees. The otherwise unoccupied interspaces are largely 

 taken up by coarse mountain grass {Epicampcs ligulata) and 

 low, thorn}' underbrush {Ceanothus fendleri). Where the pine 

 stands more closely, Muhlcnhergia gracilis takes the place of 

 many shrubs, and immediately across a V-shaped gully, with a 

 northeast instead of southeast aspect, this grass and the pine 

 have almost displaced the shrubbery and the other grass, and 

 the transition is strikingly complete. This is but one example 

 of what may be constantly observed in aspect relations, whenever 

 the opposing slopes extend in a more or less east-vv'est direction 

 laterally. We need only to climb 1,000 feet to the vicinity of 

 Mount Lemmon, to find the same grassy pine forest of the above 

 noted northeast gully slope on a mountain side facing in a south- 

 erly direction. 



In the Santa Rita Mountains a number of the character- 

 istic plants change their aspects between the lower and upper 

 limits. In ascending by the way of Stone Cabin Canyon, net- 

 leaf oak (Quercus reticulata) is first found in shaded gullies 

 and strictly north acclivities at about 6,000 feet It becomes 

 more common upward in company with the whiteleaf oak (Q. 

 hypoleuca), which appears about the same time in similar places. 

 At 6,500 feet it was seen to assume tall, clean, coppice form about 

 twelve feet high, in the gulches frequently with large, obovate, 

 flat leaves. Ascending, it increases in abundance, spreading 

 now over east and west slopes. Upon reaching Horse Ridge 

 which extends east and west at the head of the canyon at an 

 elevation of 8,000 feet,it is practically absent from the north side, 

 on the south side however.it is seen to mix freelywith the other two 

 oaks {Quercus hypoleuca and g. arizonica), displacing ih'^^iu more 

 and more as the stuation becomes higher, steeper, more rocky and 

 exposed. At length the other two are left behind, the netleaf 

 oak is the typical chaparral growth under the scattered pines, 



