THE SPINNING PROPERTIES OF COTTON 83 



they were chosen for propagation (except that it was of the 

 length required in each case), for the very good reason that no 

 such information can possibly be obtained until enough of the 

 seed is available to raise a crop under field conditions. When 

 this had been done it was found in the spinning-tests that all 

 four were equal to high grades of the equivalent commercial 

 varieties, although these are the sole survivors of a stringent 

 process of economic selection. That four random choices should 

 have been equal to, and even markedly better than, the standard 

 commercial product, is a clear indication that the mere elimina- 

 tion of gametic impurity, leaving only the irregularities due to 

 zygotic fluctuation, is sufficient to improve the strength of the 

 yarn. Confirmation of this view is found in the fact that most 

 of these pure-strain samples which spun so well had previously 

 been condemned by expert graders on the grounds of their 

 appearance and handling, owing to indifferent cultivation ; the 

 results of the spinning-tests were invariably better than the 

 handling of the sample had indicated, sometimes to a degree 

 which would have been ludicrous, had the consequences not 

 been serious. 



The question therefore arises as to the cause of this improve- 

 ment. If yarn-strength can be improved by introducing the 

 cultivation of pure strains, could not machinery be made to 

 " purify " the lint of impure varieties, and so avoid the expense 

 and trouble of organising pure-strain seed-supply systems ? 



On examining the available data from the preparatory pro- 

 cesses of spinning it would seem that the amount of waste 

 removed in carding and combing both pure and impure lint is 

 much the same ; on the other hand, since the comber waste 

 consists of short hairs, and since the frequency distribution of 

 lint-hair length has a lower coefficient of variation in the pure 

 strain, one might reasonably expect the waste to be less. This 

 discrepancy seems to indicate that much of the waste consists of 

 hairs which have been damaged in the preparatory processes 

 (from ginning onwards) and not only of hairs which were 

 initially short. The evidence regarding length thus throws no 

 light on the reasons for the superior spinning properties of pure 

 strains. 



The solution seems to be found in the breaking-strain 

 characteristic. In the past it has been rather too easily assumed 

 that differences in " fineness " of lint were equivalent to differ- 



