198 Viiirf rsili/ of Califorxiit ruhllcdtiniis hi TiotiDiu ' I Voi,. 7 



I'ro'ii widely st'pai'alcd <i('()<ii'a|)liic afciis, and ol' the many l)otaiiical 

 varieties to fnriiisli sonietliiiii: of ;i basis for the ealeidation of tlie 

 total amount of cnlilie!- pi'esent on any jrivoii area, tlie total tonnajie 

 liavin<i' been di'tei'niined in the manner just described. AVhile these 

 results are fai" from satisfactoi'X' beeause of the mea<>er data upon 

 which they are iiaserl they will fui'nish at least a b('<riniiin^ in case 

 move extensive iiivestifi'ations are inaufjurated, and will indicate the 

 best locations for rubber mills in case the p-overnment is ever oljji^cd 

 to resoi't to Rabbit -biMish as a soui'ce of rubbei- in time of emero-eney. 

 The areas indicated in the following' list include, we beliexc, most 

 of those where Rabbit-bi'ush is abundant, yet it is (piite certain that 

 at least a few larj^e areas have escaped our hasty held survey. It is 

 well know n that, in addition, there is a multitude of small fields of the 

 shi'ub and also that it often grows scatteringly whei'c other species are 

 dominant. However, because of the gi-eat expense of assembling shrub 

 from small scattered fields, this source is not included in the estimates. 



a. DISTRICT I— EAST CENTKAL CALIFORNIA ANF) A1).)A( K.\T 



NEVADA 



This district comprises Tnyo and Mono counties in California, and 

 an extension into Esmeralda County, Nevada, chiefly to include Fish 

 J^ake Valley. In it are found large areas of shrub carrying over ;! per 

 cent of rubber, although the total area of shrub is much smaller than 

 in some of the other districts where the percentage content is less. 

 The chief variety included in the estimate is viridnlus, which is larger, 

 on the average, than any of the others. It occurs chiefly on the alka- 

 line valley bottoms but ranges sparingly to altitudes of 7200 feet in 

 alkaline soil. Mixing sonunvhat with it around the borders of the val- 

 leys, where the soil is better drained and less alkaline, are considerable 

 quantites of gnaphalodcs, Jiololciicus. and mohavrusis. These extend 

 well uj) the foothill slopes but always as mixtures in the Sage-brush 

 climax — never as pure stands. North and east of Mono Lake, virididiis 

 is replaced to some extent by coHsintilis. Thei'c is also a supi)leMientary 

 supply, furnished by th(> very considerable amount of Ch ri/snllidmuiis 

 teretifolius, a low shrub carrying about 2.7 pei- cent iut)bci': but since 

 the plants are somt>what scattered it does not enter into our estinuites 

 (see p. 266). 



Some of the l)est shrub in this district is found in Owens N'allcy. 

 where it grows on most of the flats along the i-iver; in an irregular 

 strij) along the Los Angeles aqueduct ; and on isolated areas of from 



