VOL. IV.] Trees of Southern California. 333 



Valleys, and the palm and mesquite groves of the deserts are 

 examples. The belt of Blue Oak {Quetrus Engelmanni) which 

 stretches across the hill country of San Diego County, and the 

 park like growth of Quercus ui^rifolia which covers the slopes in 

 the neighborhood of Pasadena, are perhaps to be attributed to 

 the moisture supplied by the ocean fogs which roll in and con- 

 dense upon the seaward exposures which they occupy. The 

 exception to the rule is found in that peculiar forest of yucca 

 and juniper which fringes the northern base of the San Bernar- 

 dino Range from its eastern extremity to the upper end of 

 Antelope Valley, and whose existence or limitation seems to 

 have no perceptible connection with hydrographic conditions. 

 Its constituent trees are the only ones that have solved the 

 problem of arboreal growth without a continuous supply of 

 moisture. 



At higher altitudes the cooler air and greater humidity afford 

 more favorable conditions for tree growth; the chaparral itself 

 becomes denser and larger, and at an altitude of between 4000 

 and 5000 feet a coniferous forest begins which reaches nearly 

 to the summit of the highest mountains.* This belt, which 

 occupies the higher parts of the San Bernardino Range and its 

 continuation, the San Jacinto and Cuyamaca Mountains, is by 

 no means a continuous one. It rather consists of a series of 

 forested tracts limited in area in accordance with their altitude 

 and slope-exposure; some mere patches measured by acres, while 

 the largest extends from near the Cajon Pass to Grayback 

 Mountain. West of this main forest there are small bodies of 

 coniferous trees in the Cucomonga and San Antonio Mountains, 

 in the so-called Sierra Madre, and in the Liebre Mountains, and 

 to the south larger and more valuable forests occupy the San 

 Jacinto and Cuyamaca Mountains. No accurate measurements 

 of these forest areas have ever been made, and, indeed, could not 

 be made without great expense and difficulty, so rugged and 



* There are but two bald-topped mountains in the whole region; San 

 Antonio, 9630 feet high, and Grayback, 11,725 feet high. The latter is 

 pine-clad to within 200 feet of the summit, and covered with the standing 

 trunks of dead pines to the very top, so that there cannot be said to be any 

 point above tree line. 



