Table 16 



The combined action of X rays and salts of heavy metals 

 on frequency of mutation in sprouting seeds of barley 

 (based on Stadler's data, 1928a) 



Treatment 



Irradiation 



X Rays . . . . 

 X Rays . . . . 

 X Rays . . . . 

 X Rays . . . . 



Unirradiated, 

 Unirradiated. 



Chemical 



Ba (N03)2 

 Pb (N03)2 

 UO2 (N03)2 

 None 



[U02(N03)2] 

 None 



Number of 



Descendants 



[head progenies] 



136 

 133 

 194 



72 



53 

 76 



Number of 

 Mutations 



9 



9 



11 



2 





 



revealed during the growth of the self-fertilized 

 offspring of each ear. 



Fifty -three X-ray mutations were found 

 among 2800 plants in the first series of experi- 

 ments. At the same time 1500 control plants 

 failed to show a single mutation. Sixty percent 

 of these mutants were true albinos, 5% were 

 white sprouts which gradually acquired green 

 coloration in the course of their development, 

 15% were yellow (of various intensities of color- 

 ing), 10% were greenish yellow, and the remain- 

 ing 10% had various kinds of multicolored leaves. 

 The majority of these mutations were lethal and 

 nearly all of them grew very poorly. Few mu- 

 tants which reach maturity remain stable. 

 When the mutants were crossed with the con- 

 trols, the changes were transmitted through 

 the pollen, appearing as recessives in Xg. 

 Stadler considers these mutations as changes 



of the dominant gene to the corresponding 

 recessives in the somatic cells of the homo- 

 zygous plant. 



As for the effect of X rays on corn [Stadler, 

 1931a], irradiation of the embryo produces 

 chimeras at various stages of its development. 



In this paper Stadler once more raises the 

 question of the relationship between the fre- 

 quency of mutations and the intensity and wave 

 length of the X rays. The wave length was 

 obtained from unfiltered rays of 54 to 108 kilo- 

 volts. The doses were changed by varying the 

 length of exposure from 2 to 30 minutes, with 

 the other conditions of irradiation being held 

 constant (108 kv, 4 ma, 18 cm from the tube, 

 without filter). As the experiment shows 

 (Table 17), the frequency of mutations in- 

 creases proportionately to the dose. 



Table 17 



The relationship between dosage and frequency of gene mutations 

 after irradiation of [corn] seeds 

 (based on Stadler's data 1930)^ 



[These data are not in either of the 1930 papers by Stadler cited by the author. Tablets cited inStubbe (1937)]. 



36 



