28 University of California Puhlications in Botany [Vol.9 



The five stations selected, their geographical position with respect 

 to each other, and the distinctive character of the local topography, 

 are: 



(1) Summit, Nevada County, 7,017 feet elevation, lies at the top of the divide, 

 about 300 feet above Summit Valley and nearly 1,100 feet above Donner Lake 

 (5,939 feet), a glacial lakelet three miles long, draining into Truckee Kiver. 

 Lower Canadian life-zone (Pinus Jeffreyi the characteristic tree). 



(2) Fordyce Dam, Nevada County, 6,500 feet elevation, and about nine miles 

 northwest of Summit. The station lies just below Fordyce Lake, a small glacial 

 lakelet receiving drainage from the northwest side of Castle Peak and the south- 

 west slopes of Mt. Lola. The lake lies 1,500 feet below the divide, on the Avestern 

 slope of the range, and drains into the South Fork of the Yuba through Fordyce 

 Creek. The zonal position is middle Canadian (Abies magnific<i and some Pinus 

 Murrayana on the slopes above the lake.) 



(3) Tamarack, Alpine County, 8,000 feet elevation, lies on the headwaters of 

 the Mokelumue Eiver in a glaciated region with many small lakes, the largest 

 being the Blue Lakes, two glacial basins, each about one-half mile long. The 

 station is distant from Summit about 50 miles to the southeast and is in the 

 upper part of the Canadian life-zone {Pinus Murrayana dominant tree). 



(4) Tahoe, Placer County, 6,230 feet elevation, lies on the northwest shore of 

 Lake Tahoe, the largest lake of the Sierran region, some 21 miles long and 12 

 wide and very deep; it never freezes over in winter. The main divide of the 

 Sierra lies six or seven miles Avest of the station and the crest is 2,500 to 3,000 

 feet above the lake. Transition life-zone (Libocedru-s decurrens, Abies concolor, 

 some Pinus ponderosa). 



(5) Bridgeport, Mono County, 6,500 feet elevation, lies on the- east side of 

 Bridgeport Valley, a large mountain valley nine miles long and four Avide at the 

 AA'idest part, drained by the East Walker River and receiving the drainage from 

 the east slope of the Sierra through Big Buckeye and Robinson creeks as Avell as 

 some small amount from the arid mountains north of Mono Lake. About 95 

 miles southeast of Summit and in the upper Sonoran life-zone near the boundary 

 of the Transition. 



The data studied cover the years 1914-1917 inclusive. This quad- 

 rennium has been chosen for study since data from all five stations 

 exist for this period only. Inspection of temperature data shows that 

 the means of the quadrennium differ but slightly from the means of 

 much longer periods at three of the stations and that the maximum 

 variation, a December excess of 6.4° over the mean of the 12 years' 

 record, occurred at Tamarack. In no other monthly mean throughout 

 the year is the variation half as large. It is believed that deductions 

 made from the data of this period concerning the local climates of the 

 several stations are not invalidated by the brevity of the record. 



The diagram summarizes the relative temperatures of the several 

 stations and shows that in the coldest part of the year Summit is the 

 warmest station though the highest in altitude of any except Tamarack. 



