'256 r)ii}'< r.<iihi of Califorxia PnhJlcatutUR in Botanij [Vou7 



The iiioistui'c and soil ivMiiiii-cinciits have not l)('fii can'fully 

 determined. As indicated above tlie most promising- foi-ins grow 

 (111 valley bottoms where there is a moderate amonnt of moisture 

 and wliei-e the soil is moderately to stT^Jiigly alkaline. Salt-grass {Dis- 

 tichlis) is so eonnnon a concommitant of vivid nlns and consimilis that 

 its presence undoubtedly indicates favorable soil conditions. That the 

 l)lants can be grown with a minimum of i)recipitation is indicated by 

 tiieir abundance in places where the precipitation drops to below two 

 inches in some years, but in these places it flourishes only on valley 

 bottoms. The soil is always more or less sandy, but the plants grow 

 readily, or at least make a satisfactory start, in the heavy clay of the 

 botanical garden at Berkeley. 



An ecologic consideration always to be kept in mind is that Chrijso- 

 thamnus is not a strong competitor among plants. It is easily crowded 

 out by other species, especially by Grease-wood if the alkali content 

 of the soil is high and by Sage-brush if the alkalinity is slight, so that 

 the area at present covered by it could be greatly extended through the 

 removal of these more aggressive shrubs. That this is true as regards 

 Sage-brush is attested by the experience of settlers who find that Rab- 

 bit brush (especially the gray forms, e.g., ynaphalodes) almost always 

 takes immediate possession of the ground after the removal of the 

 Sage-brush. This leads to the conclusion that the present occurrence 

 of Rabbit-brush does not by any means represent the total area suited 

 to its growth. It also indicates one rather simple method of extending 

 the growth of the shrub, namely by removing its competitors. 



In case the cultivation of ('hrysothamnus is ever made a commercial 

 success, the first plantations will presumably be located where the best 

 varieties now grow wild. Aside from the assurance that such loca- 

 tions would provide the climatic, soil, and otlier requirements for suc- 

 cessful growth, this would enable the management to utilize the wild 

 shrub as a supplementary supply of crude rubber, although it would, 

 of course, carry a lower percentage than the improved cultivated 

 strains. 



It is perhaps premature even to suggest districts where plantations 

 might be located but the mention of a few may be not without interest. 

 In Owens Valley, California, for example, it happens that the city of 

 Los Angeles owns nearly 200,000 acres of land, partly covered with 

 Clirijsothamnus and not at present utilized except to a very limited 

 extent for grazing i)uri)oses. It is estimated that at least one half of 

 this is suital)le to the growth of C hrysothamnus of the virkhilus form. 



