1008 BIOLOGICAL EFFECTS OF RADIATION 



Antirrhinum. Along with normal individuals there was shown a series 

 of plants grown from seeds that had been exposed to the rays in 1918 and 

 1919. They were described as vegetatively persistent {vegetativ- 

 hartndckige) if not constant types. They were designated, "Radio- 

 morphs" (Radiomorphosen) . The variations included habitus, color, and 

 form of leaves, form and color of flowers, and reproductive organs, the 

 latter being sterile throughout. Alterations of leaf form by irradiation 

 of the vegetative points were shown by photographs. 



In the work of Stein (72) the material consisted of pedigreed plants 

 from cultures of Dr. E. Bauer. Seeds of these plants were exposed to 

 the rays and then planted, A number of abnormal types appeared, such 

 as dwarfs, small cutinized leaved plants, and plants abnormal in form and 

 color. In the small-leaved forms nondisjunction of the chromosome pairs 

 was frequently observed in the reduction division. Other irregularities 

 of mitosis in the formation of pollen grains are described. She finally 

 states that the cause of the appearance of radiomorphs is not in the 

 chromosome relations ; it must be plastic substances which have undergone 

 alteration and from which an embodiment (Verkorperung) of this altera- 

 tion results. But the nature of this alteration is not thereby fathomed. 

 We can see how it works out, but we do not know in what it 

 consists. 



Radiomorphs of different phenotype have certain characters in 

 common, such, for example, as enlarged palisade cells. Their somatic 

 tissue has the normal chromosome number. By somatic reversion 

 branches arise which look normal, but their flowers retain the sterility 

 characteristic of the radiomorphs. They have produced some mutants. 

 In no case have offspring inherited the configuration of the radiomorphs. 

 In Stein's own abstract of her 1927 work (Biol. Abst., 1930, transl. by 

 G. L. Fick), she states that "there is no positive proof that the chromo- 

 somes themselves are changed by irradiation." 



In a later paper. Stein (73) described experiments in which plants in 

 early embryonic stages were subjected to radium treatment, resulting in 

 induced somatic gene mutations, of the nature of carcinomas, in localized 

 regions. Germ cells descended from tissue containing the altered genes 

 gave rise to an Fi generation which had an inherited tendency to plant 

 carcinoma. In the Fi and F2 generations, however, lesions occurred in 

 any part of the body, while in the parental plants they occurred only in 

 tissues derived directly from regions of the embryo in which the gene 

 mutation had been induced. She interprets this not as a case of the 

 inheritance of acquired characters but of the inheritance of gene mutations 

 induced in somatic tissue. The material was Antirrhinum majus. A 

 more extended account of further experiments on the inheritance of 

 plant carcinomas in the same genus is also given by Stein (75). Here 

 she states that the heredity of these abnormalities has a chromosomal 



