1) with reduced beards, and 2) with a longer 

 ear. 



Ternovskii in 1935 investigated the character 

 of mutations induced by X rays on male and 

 female gametophytes in various stages of devel- 

 opment. Flower buds of Nicotiana tabacum , 

 Solanum melongena , and S. annuum were sub- 

 jected to irradiation (65 kv, 2-3 ma, without 

 filter, at a distance of 25 to 27 cm from the 

 anticathode). Doses were varied depending on 

 lengths of exposure from 1 to 30 minutes. All 

 plants of S. melongena died from all the doses 

 used. Fr^m S. annuum he succeeded in obtain- 

 ing one fruit with a small number of seeds. In 

 Xj, 18 plants came up and neither they, nor any 

 of the plants of the succeeding generations, 

 showed any deviations. The tobacco turned out 

 to be least sensitive to X rays and in all doses 

 a certain number of seeds were obtained. The 

 flower buds of tobacco behaved variously in re- 

 lation to the X rays. Young flower buds, i. e. , 

 before reduction -division and during it, were 

 considerably more sensitive to irradiation than 

 the more mature buds. Natural mutations in 

 tobacco are quite rare (as Goodspeed points 

 out) and in Ternovskii' s experiments from 

 36, 000 control plants not a single mutation was 

 isolated. Seeds from the irradiated buds exhib- 

 ited very low germination rates. As early as 

 the sprouting stage a number of peculiarities 

 were observed: narrow leaves, very hairy ones, 

 those retarded in growth, and ramose ones. In 

 the adult stage he observed the most varied mu- 

 tations, a fact which made the classification of 

 deviations more difficult. The different muta- 

 tions were encountered with varying frequency, 

 but the narrow -leafed form was the most com- 

 mon. In general, the number of mutations ob- 

 tained was directly proportional to the dose. 



Ternovskii set as another of his aims the 

 determination of the significance of sex in his 

 experiments. He used the following method: 

 before irradiation the flower buds were meas- 

 ured and numbered. After irradiation each bud 

 was emasculated and the anthers collected in 

 separate little packages. The pollen was then 

 used to pollinate emasculated but unirradiated 

 buds. The emasculated and irradiated buds 

 were pollinated with normal [unirradiated] pol- 

 len. In Xj 7, 305 plants were examined. The 

 total percentage of mutants from irradiated 

 male sex cells was significantly higher than 

 from the irradiated female cells. As far as the 

 character of mutations is concerned, the author 

 did not establish any differences in the descend- 

 ants of the male and female sex cells. In con- 

 trast with this, differences in variety acquire 

 great significance: an experiment in 1932 

 showed that Dyubek Nikitskii gave 44 different 

 kinds of deviation, Dyubek Gasprinskii gave 

 only 2 deviations, which soon perished, and no 

 deviations in X2. The second generation of 

 Dyubek Nikitskii very characteristically showed 

 deviations in the offspring of those plants which 



had not revealed any deviations in Xj. This 

 experiment was then expanded by the irradiation 

 of four genotypes: Nicotiana tabacum var. 

 macrophylla , var. c hinensis , Dyubek Nikitskii, 

 and a Persian varieFy. A total of 2, 800 plants 

 was used. The variety chinensis and the 

 Persian variety gave a very insignificant num- 

 ber of deviations in leaf forms. The variety 

 macrophylla did not give a single X-ray mutant, 

 but in one family a haploid was found. Analysis 

 of this material indicated that the penchant 

 towards giving rise to hereditary deviations 

 under the influence of X rays is specific for 

 the genotype. 



In general, the isolated mutants are hetero- 

 zygotes which segregate in Xg. This property 

 of descendants is explained by the fact that 

 changed sexual cells arise alongside normal 

 sexual cells due to irradiation. Various combi- 

 nations of the two gave a variable heterozygosity 

 picture inXj. Observations of Xg andXg 

 showed that extreme deviations — extremely 

 narrow leaves, variegated leaves, and white 

 color of stems — were usually not hereditary, 

 and their descendants returned to the original 

 forms. Cytological investigations showed that 

 these instances were chromosomal aberrants, 

 chiefly monosomatic ones. However, gene mu- 

 tations were also observed. In Xg, 3. 9% of 

 X-ray mutants were found. However, the per- 

 centage of mutants varied greatly, reaching 30 

 to 40% in some families. Biometric working 

 over of X3 has shown that as far as the shape of 

 the leaves is concerned the investigated families 

 have formed a new biometric series with a shift 

 toward having more narrow leaves. On the 

 other hand, hereditary broad -leafed forms have 

 also been found. Examination of stable gene- 

 mutations in X3 and X4 has shown that they have 

 a normal number of chromosomes (2n = 48) and 

 that their reduction-division is normal. Five 

 haploids were found among the irradiated de- 

 scendants of Dyubek Nikitskii and N. tabacum 

 var. macrophylla in Xj, X2, andXj. They 

 were characterized by low stature, small 

 flowers and complete sterility. Ternovskii 

 approaches with considerable circumspection 

 the use of X rays as a means of obtaining muta- 

 tions of practical value. In any case, he feels 

 that, at the present stage of development, X 

 radiation cannot replace cross breeding, which 

 leads to whole outbursts of new forms. 



Lutkov published in 1937* several articles 

 describing gene mutations produced in peas 

 and barley by X rays. As source material he 

 used in his experiments (1937*) two strains of 

 Pisum sativum . The first strain (D. S. 276) 

 was obtained from a London horticultural insti- 

 tute from Pellew, the second (D. S. 228) was 

 obtained in Holland from Wellensieck. Young 

 flower buds were subjected to radiation, the 

 dosage varying from 300 to 2500 r. The per- 

 centage of fruit set as a result of fertilization 

 by irradiated pollen fell sharply as the dosage 



41 



