630 Part IV. Chapter 4. 
Juniperus californica (as a shrub 25 per cent); agaves, cacti and yuccas, more or less arborescent 
73 per cent and other species, 2 per cent. 
San Jacinto Mountain is completely encircled by the chaparral (Upper 
Sonoran Zone of MERRIAM) which extends from its base to altitudes ranging 
from 3,000 to 7,000 feet; the upper limit is extremely irregular. Below the 
5,000 feet contour on the western side, the growth is quite uniform, broken 
only by thin lines of oaks, cottonwoods and sycamores, which follow the 
courses of the streams. Above 5,000 feet the chaparral is not uniform. 
000 feet on the western slopes occur Adenostoma fasciculatum (50 per cent), 
A. sparsifolium (25 per cent), Arctostaphylos glauca, A. manzanita, Artemisia tridentata, Baccharis 
viminea, Ceanothus crassifolius, C. cuneatus, C. divaricatus (8 per cent), C. pinetorum, Cercocarpus 
betulaefolius (1 per cent), Chrysoma pinifolia, Encelia farinosa, Eriodietyon californicum, E. tomen- 
tosum, Garrya Veatchii, Lycium Andersonii, Pentstemon antirrhinoides, Pluchea sericea, Prunus 
ilieifolia, Quercus undulata (9 per cent), Rhamnus crocea, R. ilicifolius, Rhamnus rubra, Rhus 
diversiloba, R. ovata, R. trilobata, Ribes sanguineum and Simondsia californica. 
.. Below the 3,500 eontour on the eastern slope of San Jacinto Mountains occur Ceanothus 
cuneatus, C. pinetorum, Larrea mexicana, Dendromecon rigidum, Isomeris arborea, Juniperus cali- 
fornica (60 per cent), Purshia (Kunzia) glandulosa (3 per cent), Quercus undulata (8 per cent). 
carpa, Eschscholtzia californica, Lathyrus violaceus, Hosackia (Lotus) glaber, Pentstemon antirrhi- 
noides, P. spectabilis, Senecio Douglasii and Eriogonum fasciculatum ?). 
The chaparral?) as it occurs at the base and surrounding the San Gabriel, 
San Bernardino and San Jacinto mountains is such by reason of climatic con- 
ditions. It does not owe its origin to the destruction of ‚pre-existent forest 
and subsequent deficient reforestation. The shrubs which compose it are such 
as are adapted to semiarid environments and if at any time in the past forests 
covered the chaparral areas, it was at a period so remote that no trace of 
such forests exist at the present time. 
2. Forest Formations. 
The forest growth in the San Gabriel, San Bernardino and San Jacinto 
mountains presents three general types, namely, the semiarid, subhumid and 
humid. 
Semiarid Forest Beit. The principal species of the semiarid type in the 
San Gabriel Mountains are: Alnus rhombifolia, Cercocarpus betulaefolius, 
C. ledifolius, Fremontia_ californica, Juniperus californica, Pinus attenuata, 
P. Coulteri, P. monophylla (4 per cent), Platanus racemosa, Pseudotsuga mac- 
rocarpa (80 per cent), Ouercus californica (= O. Kelloggü), O. chrysolepis, O. 
Wislizeni and Yucca arborescens.- The forest of the semiarid tracts of the 
San Bernardino Range is essentially composed of stands of Pinus mono- 
Phylla. — The thin lines and groups of trees of other species which occur 
ı) Harz, H. M.: See Bibliography p. 76. 
2) LEIBERG, J. B.: See Bibliogr. p- 76; BARBER, JoHn H.: A Glimpse of the San Gabriel‘ 
forest Reservations, The Forester IV: 240. 
