212 THE PLANT WORLD 



dense and it exhibits far less variety, being composed in great 

 part of AdcHOstoma, with scattering yuccas ( )'. ffliipplei) , 

 white sage in spots, and occasional indi^'iduals of scrub oak 

 and manzanita. 



The close proximity of the t^^'o sides of the canyon, each 

 with about the same gradient, leaves little room for doubt 

 that difference of aspect is the occasion of the wide difference 

 of vegetation that has been noted. It must be that on the 

 left side, with its southern exposure, conditions prevail that 

 even at this altitude approach in some measure the severity 

 of those of the desert, and that the great majority of the 

 plants which occur in the chaparral of the right side are quite 

 incapable of growth on the left, except in favored spots. 



In the neighborhood of Banner, between Hve and six 

 miles below Julian, at about 2,^00 ft. altitude, there are indi- 

 cations that "the edge of the desert" is close at hand. We 

 now come upon scattering indi\'iduals of several desert species, 

 the mesquite and catclaw [Acacia Greg^ii), a flat opuntia, 

 like O. Eugehnainti, one of the branching opuntias, and in 

 lower ground the desert willow {Cliilopsis insigna). 



Following the road eastward for the next three miles, 

 as it very gradually descends, it is noticeable that the live 

 oaks have dropped out and but \ery few species of the 

 chaparral are to be seen. Adoiostoma still occurs, and there 

 are occasional specimens of scrub oak and a few other 

 shrubs, but with them, forming in places a remarkably mixed 

 association, are species of Agax-f, Yucca, Krameria, Opuntia, 

 Ccrcus, and A triplex. The presence of a Juniper and a 

 plum add to the confused mixture of biological forms. Here 

 on the one hand are a few species belonging distinctively 

 to the chaparral of the mountain slopes, l)ut mingled with 

 them are a larger number of true desert plants. 



Another mile and the last vestige of mountain vegeta- 

 tion has disappeared. The creosote bush and guietta grass 

 {Ephedra) have put in an appearance, the scrub oak and 

 chamisal have fallen out, and the dominant vegetation con- 



