40 Universifij of Culifornia PuhJirafions. [botany 



spur and strike the south and southwest sides of the basin, carry- 

 ing- the temperature line, and with it the lower edge of the pine 

 belt, up on those slopes; the southwest side of Schains Ridge is 

 again protected from desert winds and, although exposed to the 

 direct rays of the sun during the hottest part of the day, it is 

 fringed by a narrow belt of coniferous forest. 



Besides the warm ascending currents we have also to consider 

 the cold descending currents. During the night the cold air 

 from Fullers Ridge and the higher mountains glides down their 

 slopes and settles in the basin known as Hurley Flat, and it is 

 asserted that on some nights there is a heavy frost at this place, 

 while at Schains, 1700 feet above, it remains frostless. The fact 

 that the bed-rock is near the surface at some places on the walls 

 of this basin should perhaps be taken into account in case a 

 detailed examination were to be made, but it does not atfect the 

 general results as noted above. 



Numerous cases similar to that just described occur all along 

 those slopes facing the Colorado Desert. It is thus seen that the 

 presence of this hot, arid region exerts no small intluenee on the 

 distribution of plants on San Jacinto Mountain. 



ROCK SURFACE, AVALANCHES, AND LAND SLIDES. 



But little of the surface of San Jacinto Mountain is devoid 

 of all vegetation. Large areas on the west side of the high 

 ridge connecting the main peak with Marion . Peak are so 

 closely covered with large rocks above the 9000-foot contour that 

 one can scarcely make his w^ay among them, yet wherever there 

 is sufficient moisture we find forests of Abies concolor, Pinus 

 Murray ana, or P. flexiUs, depending on the altitude. There are, 

 however, a few barren cliifs and rocks, some of the latter a 

 thousand feet high, in the vicinity of Tahquitz Peak and along 

 the great fault on the northeast. These stand out in bold relief 

 from the forests which surround them. 



Although there is scarcely sufficient snow on the mountain to 

 cause serious avalanches, still the extreme steepness of the north 

 side tends to their production. There have been a few of these 

 which, tearing down the north and northwest faces of the main 

 peak, plunged into the tributaries of Snow Creek Canon, leaving 



