some were semi -lethal. The author observed 

 no giant or fast growing types, or any which 

 were of any particular value because of their 

 flowers or their fruits; in short, there were no 

 superior types possessing economic significance. 



Asseeva and Blagovidova in 1935 used radia- 

 tion in order to obtain artificial mutations in 

 potatoes. Both soft (64 kv) and hard (180 kv) 

 rays were used. Mutations were found both in 

 the leaves and in the tubers. They noted an 

 interesting peculiarity in the effect of the radia- 

 tion on the tubers, specifically the importance 

 of variety [of potatoes] for the frequency of 

 mutations (Table 18). 



Tuber mutations were found only in variety 

 "Vol'tman" (five instances in 10 bushes). From 

 their experiment they drew the following con- 

 clusions: 1) the number of mutations increases, 

 generally, in proportion to the number of r; 



2) the effect of short and long exposures is equal; 



3) soft and hard rays are equally effective; 



4) irradiation at intervals or all at once does 

 not seem to have any perceptible effect on the 

 frequency of mutations. 



Haskins and Moore in 1935 observed changes 

 of growth in citrus sprouts due to action of X 

 rays. Albinism often appears in citrus plants 

 especially in hybrid lines. After irradiation, 

 however, an abnormally high percentage evi- 

 denced a lack of chlorophyll. This condition 

 varies within wide limits, from those in which 

 all green pigment is absent, through variegated 

 leaves, to full albinism. Moreover, the authors 

 observed numerous instances of terminal and 

 lateral fasciation, twisting of stems, and dupli- 



cation. For example, the last phenomenon was 

 revealed in the splitting of the central veins of 

 the leaves near the stem. In some cases, es- 

 pecially in grapefruit, the entire leaf would 

 become double. In lemons this development led 

 to the appearance of leaves with two or three 

 leaflets on the same plant. In two grapefruit 

 plants cup-shaped leaves were observed. 



Kraevoi, in 1935, irradiated a pure line of 

 Pisum sativum vulgare with a dose of 1000 r and 

 found this dose to be semi -lethal. Among the 

 progeny there appeared plants which pheno- 

 typically were completely distinct from normal 

 ones. In another experiment, following the 

 action of doses of 250, 500, and 750 r, aberrant 

 karyotypes were found. They had unpaired 

 chromosomes, which had not undergone second- 

 ary division and which were abnormally thick. 

 A certain number of aberrants remained in X3, 

 too, and for that reason the author called this 

 type the delayed modification of the karyotype. 

 He observed that as the dosage is increased, 

 the percentage of aberrants increases (Table 19). 



These plants differed in phenotype from the 

 plant from which they were derived. 



In his third article, devoted to the question 

 of the effect of X rays on plants, Kraevoi [1936] 

 raises the question of whether it is possible to 

 obtain useful mutations by the experimental 

 method, and answers the question affirmatively. 

 He points to the works of Sapegin [1930, 1934], 

 McKay and Goodspeed [1930], Horlacher and 

 Killough [1931], and also to the unpublished 

 work of Guilleminot, who obtained two useful 

 mutations from a pure strain of barley: 



Table 18 



Leaf mutations of potatoes 

 (based on the data of Asseva and Blagovidova, 1935) 



Table 19 

 (based on Kraevoi' s data, 1935) 



40 



