X-RAY EFFECTS ON O'HEEN PLANTS 975 



showed excessive branching when the young seedUngs were irradiated 

 inchided: Agrostemma, Dianthus, Viscaria, Gilia, Alonsa, Matihiola, 

 Impatiens, and Linum. 



Greater development of axillary buds of underground stems was 

 claimed by Morgan (43), who found on raying Freesia corms that those 

 receiving lighter doses produced a greater number of plants per pot. 

 While each control corm produced but a single plant, as many as five 

 shoots were produced by a single X-rayed corm. Usually only the top 

 bud developed while the others were aborted. Morgan believes that 

 raying stimulates the growth of buds other than the apical one. With a 

 heavy dose, retarding effects on growth were evident. 



Scaglia and Businco (56) found that when hyacinth bulbs were irradi- 

 ated with increasing dosages of X-rays, one or more examples out of every 

 group showed a greater development than the controls. Johnson (22a), 

 using 3500 r-units on paper-white narcissus bulbs, found that the number 

 of shoots from the treated bulbs was approximately the same as in the 

 controls, but that the former showed over 50 per cent decrease in height 

 of the shoot. The average number of leaves per bulb was somewhat lower 

 in the rayed specimens. 



The tobacco plants studied by Goodspeed (12) which survived treat- 

 ment were usually abnormal throughout. Differences in growth rate, 

 habit, leaf form, and in fertility between treated and controls were 

 evident. "A certain amount of this variation," Goodspeed and Olsen 

 (14) believe, "is a consequence of disturbance of mitotic or meiotic 

 elements or mechanisms, the results of wiiich are visible, possibly cyto- 

 plasmic in origin and directly referable to the particular character of 

 the treatment." In some cases, the normal appearance of the young 

 plant may be the result of the replacement of an abnormal by a normal 

 axis following the proliferation of an apparently unaffected, lateral bud. 

 Goodspeed figures plants from X-rayed seedlings showing dwarf habit, 

 abnormally narrow, lanceolate leaves with irregular and weak venation, 

 often notched at the top or split for more than half the length. Variations 

 in flower color, form, and fertility were also evident. 



X-rayed barley seedlings do not produce anomalies conspicuous in 

 most other plants, according to Stadler (63) who reported that in a 

 careful examination of 23,000 treated plants he found only two variations 

 affecting the tillers directly. In one plant, two of its tillers had distinct, 

 broad, yellow stripes on the leaf blades and sheath; the other plant had 

 a similar yellow stripe on the upper sheath and blade of the main stalk, 

 beginning as a narrow line but broadening on the upper leaves and appear- 

 ing on several spikelets of the head. The seeds of these spikelets gave 

 yellow, green, and sectorially yellow-and-green plants. Stadler also 

 reported the occurrence of mutant seedling characters, many of which 

 were chlorophyll abnormalities. 



