gaul: induced mutants in seed-propagated species 



231 



Table 7. — Continued. 



*Where no data are recorded the yield is lower than 80 per cent of Haisa II. All mutants 

 originated by X-rays and were selected in M; and Ma between 1954 and 195& from various experiments. 



In Table 7, heading data of 56 earliness mutants are recorded 

 which are all derived from the barley variety Haisa II. These data are 

 based on observations of at least 2 years, but in most cases the results 

 from 3 to 7 years are recorded. Occasionally, the mutants were grown 

 in the same year in two different trials and therefore the number of 

 observations recorded in Table 7 is sometimes greater than the num- 

 ber of years tested. The most extreme mutant we have is 10.1 days 

 earlier than the mother line on the average of eight observations in 7 

 years, and there are all transitions to mutants only 0.2 day earlier. 

 In each mutant the degree of earliness varies somewhat from year to 

 year, indicating the influence of environmental factors on the expres- 

 sivity of that character. It seems that the variability is usually greater 

 with more extreme earliness. 



The mutant character of 28 of these earliness mutants could be 

 firmly recognized in the M 2 generation. They may be considered, 

 therefore, as large mutations. The other 28 were either questionable 

 in M 2 or were found for the first time in the M 3 generation. Most of 



