STUDIES ES' THE EFFECT OF RÖNTGEN KAYS, ETC. 287 



The writer was spccLilly interested in tho reljition between sensi1)ility to 

 Röntgen raj-s and tlio water content of seeds, so in tho seeds their water contt-nt 

 W!is determined. As already stited, other investigators akf) jiay attention to this 

 ]X)int. For example, G. SciiwAnz (1907) says, " die Eöutgeiüichtempfindlich- 

 kcit der Zellen ist ihrer Stoüwcchselgrößo grade proportional " (p. 97'2). When 

 the amoimt of water is less, impediment appears only by a rather strong 

 doae, and vice versa. Tliis fact is also observed by Koernicke (1915) " auch 

 der Plasmareichtima imd Wassergehalt dor Zellen muß bei der eventl. Lösung 

 dieser Frage iu Betracht gezogen werden " (p. 429). Therefore, Schwakz's 

 result on the 200H-seeds of Vicia faba, which developed just as the unirra- 

 diated controls did, is open to doubt. In Koernicke's experiment, an 

 impediment of gi-owth apjxsars at 50 H in the case of air-dried seeds. 

 The rektion between setsibüity to ßüntgen rays and water content of seeds 

 at the time of irradiation is important and of interest. But these authors did 

 not indicate exactly the water content of the seeds used, so tLat their results 

 cannot be directly comjmi'ed with those of the writer. 



KoEENlCKE states that only Vicia fala among ten kinds of experimental 

 plants was afl'ected bj- X-rays, the others showed neither a jwsitive nor a 

 negative effect, and the germination of cereals, in particular, is not accelerated 

 nor is there any effect in their growth, but the writer observed the acceleration 

 of gennination in OrijZa saliva^ and Pliaseolus vulgarür (white seeded varieties). 

 Therefoi-e he cannot agree with him. 



Plants differ in sensibility to Röntgen rays accordiug to tho sj^jecies. 

 In other words, plants make selective absorption. So the writer thinks the 

 effect cannot be definitely stated as regards a cei-tain plant, unless a hirgo 

 numljer of experiments have been made. 



The following are the s^iecial results obtained from tho writer's exj^ierimeuts : — 



(1) Though tho seeds are exix>sed to Röntgen rays of high dose, their 

 development is not stopped imtmedLately. They germinate and develop for a 

 certain period. 



(2) Though the impediment of growth Ls caused by the dose which is 

 inversely proportional to the water content of seeds, the injured plants cease 



1- In air-dried irradiated seeds, 5H-10H was the effective dose for acceleration. 

 2. Of 5H-, lOH-seeds, the germination ef the SH-seeds was accelerated. 



