WHALEY: RUBBER 25 



native dandelions. It is distinguished by the character of its involucral bracts 

 and by the shape and size of the leaves. 



The Russians began to cultivate kok-saghyz shortly after its discovery by 

 the Ketman expedition. They achieved some considerable measure of success 

 although its domestication in Russia, as in this country, has involved many 

 problems. 



A shipment of kok-saghyz seed arrived in this country in May 1942 and 

 was distributed to various cooperating agencies and stations of the Bureau 

 of Plant Industry for planting. Work of the last two years has indicated that 

 kok-saghyz can be grown successfully in certain areas within this country and 

 that with the solution of certain fundamental problems the plant would 

 represent a valuable source of rubber. 



As to its distribution it is now apparent that good growth of the plant in 

 cultivation can be secured during the summer only in regions far enough 

 north so that they do not have continued periods of exceedingly high tem- 

 peratures. The best growth is of course in regions having relatively, not 

 excessively, high day temperatures alternating with low night temperatures. 

 Within this country the areas around Lake Champlain. in Northern Vermont, 

 the Saginaw Bay area of Michigan, and the Red River Valley of Minnesota 

 have been found to give very good results as to root growth. Best seed yields 

 have been obtained at high elevations in intermountain Rocky Mountain 

 valleys in Montana. 



The Russians have reported 27 to 30 pounds per acre of seed as represent- 

 ing excellent yield. Montana yields are in excess of 150 pounds per acre. 

 Some of the plants in that region have shown as many as 500 flowers during 

 a season with as many as 100 in bloom at one time. 



The problems incident to cultivating kok-saghyz include many of funda- 

 mental biological interest. Plantings grown from the seed which was im- 

 ported from Russia contained plants ranging in rubber content from tenths 

 of a percent to 16 or 18 percent, and in the case of some Canadian grown 

 material up to 29 percent in the second year. Such a situation offers a tre- 

 mendous opportunity for improvement by selection. Improvement by selec- 

 tion alone necessitates the building up of clones of the selected material by 

 vegetative propagation. 



Vegetative propagation of kok-saghyz has presented numerous problems 

 for solution. Early experiments with root cuttings in the greenhouse, tended 

 to indicate that the matter of making root cuttings and growing plants from 

 them was fairly simple. Attempts to repeat the procedures in the fields were 

 very unsuccessful. Several factors now seem to be concerned. In the first 

 place the amount of available stored nutrient material is a controlling factor. 

 There is a wide variation in the amount of this material in different parts of 

 the seasonal cycle. It now looks as though root cuttings would either have to 



