146 OUTLINE OF PLANT GEOGRAPHY 



ary. The range is less definite at the north, merging into the 

 Cascades of southern Oregon. Southward from Mt. Shasta it 

 is more clearly defined and forms the eastern boundary of the 

 great central valley. The mountains rise rapidly from the level 

 valley floor, and as one ascends, a marked change is noted in the 

 vegetation. 



Along the upper Sacramento, and in the vicinity of Mr. Shasta, 

 the Douglas fir is the commonest tree, and the general type of the 

 moist forest is much like that of Oregon and Washington. The 

 flowering dogwood and vine-leaved maple are common and along 

 the Sacramento river one sees bushes of syringa (Philadelphus), 

 and Calycanthus. This region is the home of the Calif ornian 

 pitcher plant (Darlingtonia). 



The foot-hills of most of the great valley are grass covered, and 

 with an open growth of oaks, buckeye, and various shrubs, often 

 forming chaparral formations of greater or less extent. The chap- 

 arral shrubs are much the same as on the coast ranges, e. g., Man- 

 zanita, Ceanothus, Rhus, Ribes, Rhamnus, Eriodictyon, etc. 



The first conifers to appear are " digger-pines " (Pinus Sabi- 

 niana), curious thin-leaved, gray open-branched trees, characteris- 

 tic of the dry belt which in parts of the range occupies the slopes 

 above the lower foot-hills. 



At about 2,500 feet the yellow pine (P. yonder osa) begins, and 

 at about 4,000 feet in the middle Sierra, one enters the magnificent 

 belt of mixed coniferous forest, which is perhaps without a rival 

 anywhere in the world. 



Below this zone, and sometimes extending into it on dry and 

 exposed slopes, are extensive chaparral formations made up of 

 a good many species. Manzanita (Ardostaphylos spp.), Ceano- 

 thus, scrub oaks and chinquapin (Castanopsis) are the most 

 abundant chaparral shrubs, but there are a good many others 

 mixed with these. Among the less common but very showy shrubs 

 may be mentioned Fremontia Calif arnica (Sterculiaceae), with 

 big yellow flowers, and the rare Carpenteria Calif arnica with 

 very handsome white flowers. This chaparral covers great ex- 

 panses of the dry mountain slopes and is often quite impenetrable, 

 the tough interlacing branches making an impassable thicket. 



At about 4,000 feet, the main forest zone begins. This is well 

 shown in the Yosemite valley. At this elevation the yellow pine 



