244 The Plant World. 



arizonica, seen Trst in shaded, northerl\' places, soon lecame in- 

 creasing! pre.alent, v as still occasionally present high up on 

 the south, est side of i.incon leak, but consistently absent from 

 the steej), north est slope taken l)y its tvv o congeners next higher 

 in range. J eturning to the Manning Trail, it is first met on 

 the shad;- side of a rocky projection at about 5,400 feet in as- 

 cending, and on the first sunny slope below the pine forest in 

 descending. Cn the other route, Quercus hypoleuca first ap- 

 peared on a steep northwest ascent with Ceanothus jendleri at a 

 point between 6,500 and 7,^00 feet, ushering in true chaparral. 

 It is the principal constituent of large bodies of chaparral thence 

 upward, continuing almost to the summit, but above the limit 

 of the Arizona pine is more and more displaced by Quercus 

 reticulata. It approaches the ultimate summit only on the most 

 direct south slopes, w here it is still a little taller than its more 

 numerous neighbor last named. Again returning to the Manning 

 Trail, it first shov. s itself on the left or northwest side of the ridge, 

 and barely disappears from the austral side of the hills before the 

 summit is reached, though replaced by the herbaceous plants of 

 the pine forest on boreal aspects. Its companion, Q. reticulata, 

 appears on this route in similar northerly and otherwise sheltered 

 situations, displacing the other more and more on the higher 

 slopes toward Mt. Ochoa. Given similar topographic conditions, 

 one or both together replace the pine invariably on the most 

 southerly aspects. The same is true at similar altitudes in the 

 Chiricahuas and the Santa Catalinas. On the Rincon Peak 

 ascent, the netleaf oak was not seen until reaching the shade of 

 the pines, but above the more level pine forest it formed dense 

 bodies of typical and almost insurmountable chaparral on the 

 steep slopes^ either loose or rocky, approaching the summit on 

 the south as well as the northwest side. It was especially tall 

 on the latter aspect, being here diversified by an occasional 

 small Douglas fir and Mexican white pine. It remained the 

 principal part of the chaparral to the ultimate summit at 8,465 

 feet. On the razor-edge crest dropping eastward just under the 

 summit, however, it was absolutely confined to the dense ever- 

 green chaparral on the open south side. The north side, partly 

 enclosed by precipitous crags, in the complete absence of the 

 chaparral, was possessed to the very edge by the two coniferous 



