UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



BOTANY 



Vol. 7, No. 8, pp. 265-278, 2 figures in text November 7, 1919 



ITL THE OCCURRENCE OF RUBBER IN 

 CERTAIN WEST A^EERICAN SHRUBS 



BY 



Harvey Monroe Hall and Thomas Harper Goodspeed 



CONTENTS 



PAGE 



I. Chriisothamniis (exclusive of C. nauseosu^) and HapJopappus 265 



11. Reg-ional rlistribution of rubber in Haplopappus 274 



III. Species iu which no ruV)ber is found 276 



I. CHRYSOTHAMNUS (EXCLUSIVE OF C. NAU8E0SU8) 



AND HAPLOPAPPUS 

 In a foregoing report attention has been paid almost exclusively to 

 rubber as it occurs in the numerous varieties of Chrysothamnus naiis- 

 cosns. In the course of the investigation we have also examined as 

 many of the botanically related species and genera as were readily 

 obtainable as well as some species of shrubs not closely related to 

 Chri/sothannius. The total number of species of woody plants exam- 

 ined is seventy-nine. As a result of these examinations rubber is now 

 known to occur in four other species of ChrijsotJiammis and in ten 

 species of Haplopappus. In no case, however, were we able to detect 

 rubber in any plant other than those showing a close botanical affinity 

 to Chrysothcnuius. Those in which rubber was found are indicated 

 below. In the tables the percentage of pure rubber is indicated by 

 the benzene extract. All percentages are based upon dry shrub except 

 where "x" indicates that no moisture determination was made. 



Chrysothamnus turbinatus (IM. E. Jones) Rydb. 



The general habit and appearance of this species is. very much 

 like that of certain varieties of C. nauseosus. Although it differs from 

 that species in what appear to be important technical characters, such 

 as the elongated, columnar involucre, it is not unlikely that further 



