1919] Hall-Goodspccd : Ckrijsil 209 



places averaged less than 1 per cent of rubber and nowhere did we find 

 other than small groups of the plants. A single sample of frigidus 

 from Laramie, Wyoming, was found to carry 1.86 per cent of rul)ber. 

 A sample of pinifolius from Salida yielded 4 per cent. 



Our estimate of the total amount of rubber present in Chnjso- 

 thamnus in Colorado is based entirely upon Avhat was found in the San 

 Luis Valley and is therefore, as indicated above, about 24,300,000 

 pounds. 



//. ESTIMATES NOT IXCLUDED IX THE ABOVE DISTRICTS 



There are many districts in addition to those just enumerated 

 that will need to be explored before a final statement as to the occur- 

 rence of rubber-bearing shrubs can be made. Large bodies of these 

 plants might be found in any of the western states. The most promis- 

 ing of these, in addition to those already specifically mentioned, is per- 

 haps Wj-oming. It is well known that this state supports large areas 

 of Kabbit-brush but aside from a few samples taken along the southern 

 border Ave have made no study of its rubber possibilities. "We have 

 been told also of considerable areas in southern IMontana, in Idaho, 

 and in eastern Washington, but judging from the varieti(^s there pres- 

 ent the percentage of rubber in the plants is very low. In Nevada, 

 which we have eovei'ed as well as any other state, there are still some 

 promising unexplored fields. Chrysothamnns occurs in a number of 

 species and varieties in New Mexico, according to good authority,^ ^ but 

 we have scarcely considered that state. Professor A. 0. Weese reports 

 a great deal in the region around Albuquerque. Arizona is likewise a 

 state of possibilities, but the areas of Rabbit-brush to be found there 

 are probably quite limited in extent. Tliese two southerly states should 

 be carefully explored in case a search is made for new strains of high 

 quality, since a considerable number of species and variants not yet 

 examined are known to occur and tlie climatic conditions are such as 

 would be expected to result in the formation of rubber. 



(. CONCLUSIOXS AS TO THE QUANTITY OF EUBBER OBTAINABLE 

 As previously noted, the explorations in search of rubber plants 

 have not extended to all parts of the West, nor, indeed, has any single 



11 Vernon Bailev. Life Zones and Crop Zones of New Mexico. N. Am. Fauna, 

 no. 3.5 (1913), pp. "28. 31, 37. 



Wooton and Stamllev, Flora of New Mexico. Contril). T^. S. Nat. Herl)., vol. 

 19 (1915), pp. 660-(563.* 



