COMPOS I TAE 



Another Daccharis which is quite widely distributed in Arizona 

 at altitudes 4,000 to 7,000 feet, is B» pterinoides , Yerba-depasmo. 



It is commonly found in excellent grass land and is never browsed 

 except in times of extreme drought. It is reported to be one of 

 the worst poison plants in the southwest. It is used as a remedy 

 for chills by the Indians and Mexicans. 



Sclidago spp. There arc several species of Goldcnrod in the 

 southwest. Seine of them extend far to the north while others are 

 confined to the southwest and Llexico. For the most part they are 

 good erosion control plants but valueless for forage. Our chief 

 interest in them at present is for their rubber content. Some 

 species seem to run four or five percent rubber and such plants are 

 comparable to guayule. None of the species are adapted to use in 

 the extremely dry, desert regions but some are suited to the Juniper 

 and Pinon belts. 



Parthenium argenta bum, the Guayule, sometimes called the 

 Mexican rubber plant, is a low composite shrub with divided, grayish 

 leaves end small whitish, rather inconspicuous flowers. It is a 

 native of western Texas and northern Mexico and has been introduced 

 extensively into California, and southern Arizona. The main intro- 

 duction in southern Arizona was made some years ago by the Conti- 

 nental Rubber Company about twenty miles south of Tucson. This 

 company made elaborate provision for growing the Guayule in quanti- 

 ty under irrigation. It, however, failed to produce adequate rub- 

 ber when given the added moisture and the project was abandoned* 

 In no place in this section does the Guayule seem to have escaped. 

 Plants arc still growing experimentally at Las Crucos, New Mexico 

 and at the Soil Conservation Service nursery at Tucson, as well as 

 on the Continental .Rubber Company plantings in southern California. 

 It has been reported that the Guayule is being very successfully 

 grown in portions of Russia and that the Soviet Republic is extract- 

 ing rubber from it satisfactorily. It seems unlikely that this 

 plant will ever be used extensively for the production of rubber 

 within continental United States unless perchance future wars cut 

 off the supply from tropical regions. Even in this case it seems 

 likely that other plants such as some of our milkweeds, spurges 

 and goldcnrod s, may prove to be even better for rubber production 

 than the Guayule. 



Parthenium incanu m, False Guayule, is a low shrub closely 

 resembling the Guayule. It is abundant in western Texas, southern 

 New Mexico, southern Arizona and northern Mexico. It has practical- 

 ly no rubber content but grows sufficiently abundant in places to 

 be a fair ground cover. It should, however, bo considered a pro- 

 duct of overgrazing and replaced by more valuable plants. It is 

 quite unpalatable. 



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