202 



GUIDEBOOK 01* THE WESTERN UNITED STATES. 



Summit 



the summer, 



feet higher.^ At the higher eleTations a large pro- 

 precipitation is snoWj as it rarely rains much during 



summit the snow may accumul 



of 20 feet on the level during a single winter. 



XLVII 



On the west slope of the range, between the elevations of 6,000 

 and 7,500 feet, is the great Sierra forest zone, although the full 

 grandeur of the forest is not displayed along this particular route. 

 A note on the principal trees to be seen between the summit of the 

 Sierra and San Francisco Bay has been kindly supplied by Prof, 

 W. L. Jenson. of the UniversitA^ of California.^ 



^ The mean anmial precipitation at sev- 

 eral places along the route is shown by 

 the following table compiled from records 

 of the United States Weather Bureau ex- 

 tending over periods of 30 years or more: 



Mean precipitation on Sierra slopes along 

 line of Southern Pacific Railroad. 



Inches. 



Reno, Nev 8. 65 



Boca, Cal 20.84 



Truckee, Cal 27.12 



Summit, Cal 48,07 



Cisco, Cal 52.02 



Blue Canyon, Cal 74. 22 



Towle, Cal 59.38 



Colfax, Cal 48.94 



Auburn, Cal 35.13 



Sacramento, Cal 19. 40 



* At the summit of the Sierra are found : 

 Jeffrey pine (Pinus jcffrcyi)^ a near 

 relative of the yellow pine having a red, 

 rusty, or wine-colored bark and a large 

 cone suggestive by its outline of an old- 

 fashioned beehive. 



Wliitebark pine {Pinus albicauli^), a 

 timber-line tree, dwarfed and often pros- 

 trate, commonly associated with the 

 Jeffrey pine. 



Tamrac pine {Pinus contorta var. mur- 

 rayana), found chiefly at the higher alti- 

 tudes and especially abundant in swampy 

 meadows, but grows also on the granite 

 ridges and is frequently a timber-line 

 tree. It is characterized by its short 

 foliage consisting of two needles in a place 

 and by its small burrlike cones. This 

 tree is not the eastern tamarack. 



Western juniper (Juniperus occiden- 

 talid)j a very characteristic tree of granite 

 ridges and cliffs. 



On the middle western slope the four 

 prevailing species, which can probably 

 be recognized from the train, arc: 



Yellow pine {Pinus ponderosa), the 

 dominant tree of the Sierra forest belt and 

 on the average the largest tree, except the 

 big tree {Sequoia ^vashingtoniana or gigan- 

 tea)j which is not of general occurrence. 

 The yellow pine is distinguished by its 

 yellow bark, which is cheeked into large 

 plates 1 to 3 feet long and 6 inches to 1 or 

 2 feet wide, slightly resembling the back 

 of an alligator. The cones are ovoid and 

 about 3 to 5 inches long. 



Sugar pine {Pinus lamhcrtiana) , usually 

 associated with the yellow pine, occurs 

 in the 



forest belt; distinguished by 

 its fiuvdy checked bark, by its cones 12 

 to 16 inches long, and by the very notice- 

 able feature that the branches in the very 

 top run out into a few unequal horizontal 

 arms. 



Incense cedar {Lihocedriis decurrens), 

 the only cedar-like tree at middle alti- 

 tudes; has a reddish fibrous bark and for 

 that reason is sometimes mistaken for the 

 Sequoia by the amateur. 



WTiite fir {Abies concolor), a common 

 tree on the lower slopes below the main 

 summit, mostly associated with the yellow 

 pine. These trees will probably attract 

 attention because of the beautiful sym- 

 metrj^ of their crowns, gently tapering to 

 a pointed top. Their brancbes expand 

 horizontally and impart a stratified or 

 layered appeamnce to the crown. On 

 the higher slopes of the Siorran axis this 

 species is replaced by the red fir, which is 

 similar in appearance but has a reddish 

 instead of a whitish bark. 



