268 University of California Puhlicotions in Botanjj [Vol. 7 



Chrysothamnus linifolius rji-oovic. 



This is perliaps only a variety of ('. viscidi/l'iriis l)iit it (litlfcrs from 

 all otlu'i' forms of that cxceodinwly vai'iablc species in tiie taller and 

 more robust habit (the woody stems are sometimes eight feet hig^h), in 

 the broadly linear leaves, and in the greenish thiekened tips of the in- 

 volucral bracts. Its ecologie liabitat is also ditferent, since it grows 

 only in alkaline soil, whereas the forms of viscidi/fonis are confined to 

 well drained, non-alkaline slopes and benches. Tliis may account for 

 the occurrence of rubber in linifolius, and its absence in viscid iflonts as 

 well as in two othei- very closely related upland species, namely, 

 linmilis and piih( ndtis. This is in accord with what has been found in 

 C. nauseosHs, in which species, as noted elsewhere,^ the varieties carrj'- 

 ing the most rubber are all inhabitants of alkaline soils. 



Only two samples of linifolius have been examined. One (4()()) 

 from an alkaline flat near Grand Junction, Colorado, yielded on an- 

 alysis 1 per cent of rubber. The other (515), which was gathered at 

 Green River, Utah, was not analyzed. A microscopic examination failed 

 to detect any rubber in it. 



Haplopappus nanus D. C. Eaton 



The stems of this species are very low, one foot or less in height, 

 much gnarled and branched and with numerous short leafy twigs. 

 They have a thick, corky bark and a considerable portion of the wood 

 is dead in many of the plants. The foliage is deep green and (juite 

 resinous. Average plants will weigh about one pound l)ut it is usually 

 impossible to obtain the whole plant since the roots are tightly held by 

 the rocks in which they grow. The species inhabits rocky ledges and 

 outcroppings and may be expected on almost any of the mountaiii 

 ranges of the Great Basin area. It is known to grow in such situations 

 from Mono County, California, to southwestern Utah and north to 

 Washington. Wherever we have found it during tlie course of these 

 investigations it was growing in only limited quantities and there are 

 probably no considerable stands of it anywhei-e. (See fig. 2.) 



The percentage of rubber in Haplopappus nanus is Ihc highest 

 kn(jwn for any native American shrub except Guayule, our analyses, 

 four in number, indicating that it runs from 6 to 10 per cent of the dry 

 weight of the entire plant. The (piality of the product would i)i'obably 

 be inferior to that of the viridulus form of Chrysothamnus because of 

 the large amount of resins present. A sample was worked out mechan- 



iSee p. 245. 



