UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



BOTANY 



Vol. 7, No. 7, pp. 183-264, plates 18-20, 6 figures in text November 7, 1919 



IT. CHKYSIL, A NEW liUBBER FROM 

 CHRYSOTHAMXrS NArSEOSUS 



BY 

 HARVEY MONROE HALL axd THOMAS HARPER GOODSPEED 



CONTENTS 



PAGE 



I. Object and scope of the investigation 184 



II. Acknowledgments 186 



III. Nature and prop':^rties of Chr_ysil 188 



IV. Botanical classification; the names of the plants 189 



V. Chrysothamnns nau.'ieasu!^: habit, flowering, rate of growth, etc 191 



VI. Distribution and habitats of the various forms 194 



VII. Estimates by districts of the amount of Chrvsil available in western 



North America 107 



a. District 1. East central California and adjacent Nevada 198 



b. District 2. Mojave Desert, California 200 



c. District 3. Northeastern California and adjacent Nevada and 



Oregon 201 



d. District 4. West central Nevada 202 



e. District .5. Northern and central Nevada 204 



/. District 6. Utah 207 



g. District 7. Colorado 208 



h. Estimates not included in the above districts 209 



i. Conclusions as to the quantity of rubber obtainable 209 



VIII. Methods of detecting the presence of rubber and determining its nmnunt . 210 



a. Microscopical methods 210 



b. Chemical analysis 216 



IX. Results of the chemical analyses and microscoi)ical examinations; tal)ula- 



tion of percentage of rubber in each variety 226 



X. Distribution of rubber in the plant 234 



a. Regional distribution in the plant 234 



b. Specific distribution in mature tissues 239 



XI. Factors influencing rubber content 243 



a. Variation with the botanical variety 243 



b. Variation due to environment 245 



c. Seasonal variation 246 



XII. Methods of harvesting: season, age, depth of cutting, etc 248 



XIII. Possibilities of Chrijsnthamnus as a cultivated plant 251 



XIV. Cultural requirements 2.55 



XV. Summary 257 



