Vol.1] Hnll. — Botanical Surrey of San Jacinto Mountain. 13 



from 8000 to 7000 feet. At the eastern base it gives waj^ to the 

 Lower Soiioran of the Colorado Desert, but on the other sides it 

 spreads out over an extensive foot-hill region except where 

 bordered by the cultivated areas of the vSan Jacinto plains or of 

 San (xorgonio Pass. The line marking the upper limits is 

 extremely irregular since, by the effect of slope exposure, desert 

 winds, and other factors it is carried well up into the body of the 

 Transition at numerous places, while that zone makes not a few 

 dips along the streams and where protected by ridges. Of the 

 many species of shrulis w^hich are characteristic of this zone the 

 most useful as a zone indicator is the Chamisal {Adenostoma 

 fusciculatum) . The following also belong here: 



PLANTS RESTRICTED TO THE UPPER SONORAN ZONE. 



Adenostoma faseiculatum Esehseholtzia Californica 



A. sparsifolium Lathyrus violaceus 



Aretostaphylos tomentosa Lotus glaber 



Cereocarpus betultefolius Pentstemon antirrhinoides 



Dendromeeon rigidum P. spectabilis 



Dicentra chrysantha Senecio Douglasii 



Diplacus lojigiflorus Solanum Xanti glabrescens 



Eehinocystis maerocarpa Umbellularia Californica 



Eriodictyon tomentosum Eriogonum faseiculatum 



TRANSITION ZONE. 



The Transition is the largest and most important of all the 

 zones on the mountain. As shown on the map of life zones 

 (plate ii), it is comparatively wide on the west side, much less 

 so on the east, and extremely narrow on the northeast. This 

 is, of course, due to the peculiar topography. On the west the 

 descent is rather steep, but quite uniform, while on the north- 

 east there is a fault at about the upper limit of the Transition 

 Zone. Round Valley has an altitude which places it in the 

 Canadian, but from its northeast rim there is a sudden — almost 

 vertical — drop of nearly 8000 feet to the barren Colorado Desert. 

 Consequently it is but a short distance from the Canadian flora 

 of Round Valley to the Sonoran flora of the desert side of the 

 mountain. On the north side of the main peak this is carried 

 to an extreme, there being an abrupt descent from the summit 

 which, as will be shown, is within the Alpine Zone, to the west- 

 ern arm of the Colorado Desert, the flora of which is Lower 



