X-RAY EFFECTS ON GREEN PLANTS 977 



McKay and Goodspeed (38), working with cotton, found that in 

 fruits obtained from X-rayed pollen and untreated eggs there was a 

 decrease in number of seeds per fruit as the dosage became heavier. 

 Only 21 plants were produced from over 150 seeds, giving further evidence 

 that sterility is a by-product of X-ray treatment. These same authors 

 reported that striking morphological alterations were carried over to 

 the next generation, for they were found in cotton plants produced by 

 seed from plants derived from X-rayed pollen and untreated eggs. 

 Some of these alterations were the presence of twisted and deformed 

 stigmas, anastomosing leaf veins, peculiarities in leaf shape, fasciated 

 and enlarged stems, incomplete flowers, and dwarfness in habit. 



HISTOLOGICAL EFFECTS 



The comparatively few writers who have investigated the histological 

 changes which occur in tissues subjected to X-radiation have concluded 

 that the stems of treated plants show an early maturity, as indicated by 

 the advanced development of woody tissues. 



Altmann, Rochlin, and Gleichgewicht (1), in making a microscopic 

 examination of the irradiated stems of Phaseolus vulgaris, found a greater 

 development of mechanical tissue than was present in the controls. 

 The xylem w^as increased at the expense of the pith. Similar results were 

 reported by Johnson (19) who found that an increase of xylem with a 

 corresponding decrease of pith cells was apparent in the hypocotyl 

 region of mature Helianthus plants grown from irradiated seeds. In 

 cross sections from the hypocotyl regions of irradiated material, the pith 

 cells were much smaller in diameter and were thicker walled than in 

 control stems. The elements of the xylem in the former were much 

 smaller in diameter and were arranged more compactly. Even in 

 seedlings nine days old, a striking difference was shown in the amount 

 and character of xylem. There was a much greater percentage of xylem 

 in the irradiated specimens, with individual cells showing a similarity in 

 size rather than the wide diversity in size of cells which is typical for 

 xylem of young Helianthus stems. Miege and Coupe (41) likewise found 

 the vascular tissue of Raphanus and Lepidium more developed in rayed 

 plants. 



Tissues of irradiated roots of V. Faba early took on a permanent aspect, 

 according to Nakagawa (44). The greatest changes occurred in the 

 growing point, including endodermis and dermatogen; the plerome 

 suffered least. 



Cross sections of leaves of tobacco plants from germinating seeds 

 which were X-rayed exhibited various structural peculiarities, according 

 to Goodspeed (12). Cell number, form, and arrangement were the 

 same in treated and control plants, but increase in cell volumes in the 

 treated material accounted for the abnormal leaf thickness. More 



