WHALEY: RUBBER 27 



place. Once planted a serious problem arises from the fact that growth of the 

 seedlings is so slow that weeding must ordinarily be done at least once before 

 the seedlings are large enough to distinguish from weeds, or even up so as to 

 permit detection of the rows. Attempts have been made to overcome this 

 difficulty by using transplants and root cuttings. However, the solution prob- 

 ably lies in careful cultivation practices and the selection of more vigorous, 

 more uniformly germinating stock. 



Kok-saghyz is harvested by digging the roots after removal of the tops. 

 The roots are then dried and the rubber is extracted by milling the dried 

 roots. The extraction process is simple and inexpensive and the rubber ob- 

 tained, according to all tests made to date, is of excellent quality, comparing 

 favorably with good grade Hevea sheet. 



The utilization of two by-products is possible. The roots contain at harvest 

 time upwards of 8% inulin. The extraction and utilization of this carbohydrate 

 will, according to Russian work, pay for the processing cost of the rubber. 

 In addition 7 or 8% pectin is contained in the roots and its utilization has been 

 suggested. 



Other Plants. Many other plants yield rubber, some of them in appre- 

 ciable amounts, but the ones mentioned seem to offer the only possibilities as 

 rubber sources in the Western Hemisphere. Mention ought to be made, per- 

 haps, of the fact that Russians have actually grown small plantings of 

 certain species of Scorzoncra for rubber production. 



The Canadian Department of Agriculture is experimenting quite exten- 

 sively with one of the milkweeds, Asclepias syrica. A suggested procedure 

 here, however, is not to attempt to extract rubber itself, but to extract the 

 rubber and resin compound from the leaves and utilize it as a combining 

 agent with various synthetics. 



Conclusions. It is perhaps of interest to attempt to gain as comprehen- 

 sive a picture as possible of the parts played by this work on rubber plants in 

 the present emergency and in the economic and social picture of the future. 

 We were, at the end of 1941, cut off abruptly and almost completely from 

 our source of a material which has come to play a very large part in our 

 lives, both in war and in peace. We had on hand a rather limited supply of 

 that material. The Rubber Conservation Program and the rapid and success- 

 ful development of the synthetic rubber industry has turned the trick to the 

 extent of preventing a complete breakdown in essential military and civilian 

 transportation and in other processes so dependent upon rubber. 



In 1941 it was imperative that we investigate all possible sources of natural 

 rubber even though it was readily recognized that many of them could con- 

 tribute very small amounts of rubber at a very high cost per pound. This 

 was insurance against the possibility that for one reason or another the syn- 



