1919] Hall-Good speed: Chnjsil 207 



would be 23,700,000 pounds of pure rubber. It must be borne in 

 mind that these estimates are based on the weight of plants after the 

 removal of the foliage and of all stems under four years of age. 



/. DISTRICT (5— UTAH 



Within the state of Utah, Rabbit -brush in several forms occurs 

 over extensive areas, especially around the alkaline valleys of the cen- 

 tral and southeasterly parts of the state. Much information as to the 

 location of shrub in quantity has been assembled by Professor Marcus 

 E. Jonf s, but an examination of the samples supplied by him indicates 

 that the rubber content is less than that of plants from Nevada and 

 California. The analyses we have made of his plants average only 1.12 

 per cent for the consiniilis variety, which is by far the most abundant 

 one, but this is perhaps too low an average for all of the Utah shrub, 

 since three samples of consimilis collected by ourselves near Stockton 

 carried 1.31, 2.46, and 2.84 per cent of rubber, respectively. What- 

 ever the exact average may be, it certainly is low and renders unneces- 

 sary the publication of detailed information as to distribution. The 

 largest areas of shrub in Utah lie along the alkaline flats of Sevier 

 Valley, Tooele Valley (and south to beyond Vernon), Tintic Valley, 

 Rush Valley, Utah Valley, Juab Valley, and the valleys of the Price 

 and Green rivers. B}' far the largest stand of shrub is along the 

 Sevier River, where Professor Jones finds a strip about one-f(mrth 

 mile Mnde by one hundred and fifteen miles long, extending from 

 Panguitch north to Fayette, and he describes other large areas in that 

 valley. In the vallej's of northeastern Utah, such as the Uinta Basin, 

 Chrijsothamnus occurs only in small, isolated patches and is of no 

 importance in preparing estimates. In northwestern I^tah, the varie- 

 ties present are those which carry but little if any rubber and tliere 

 are no extensive areas even of these. To the southwest, however, there 

 are some stands of consim.ilis that should be taken into account. There 

 is one area of at least 20,000 acres along the line of the Salt Lake Rail- 

 road and farther south than any of those mentioned above. Tlie 

 shrubs are closely placed but quite small, the average weight being 

 estimated at scarcely over one pound. A sample taken at Milford 

 yielded 1.24 per cent of rubber. A single sample of ('. tiirhinatus 

 gathered on the plains near Lund analyzed 4.88 per cent of rubber. 

 This species is too scarce to be of impoitance save as a starting point 

 in breeding experiments. 



