268 HIDEO KOilURO. 



as3umptiou of the writer, tliat of strongly invxiiated seeds more remained, 

 except one of the 40 H- plants. 



The seeds used in Esjierimeuts I iind 11 -uere iiTadiated at the same 

 time and separcited into two paiis, one was used for field cultiu'e and the other 

 for put culture. Of these seeds, whose water content reached 57.49_%' by 4G 

 hom's' steeping, the majority of the 40 H showed the tip f>f the radicle to 

 sippear out of the seed coat ; they also swelled very much compared with the 

 others. 



Experiment III. 



The seeds were steej^xjd in water for 31 hours (when the water content 

 reached ÖO.OS^) and ex^xised to the rays of 20H, 30H, 50H, 60H, 80H, 

 100 H, 120H and 155 H on March 31, 1917. Of 20 seeds of each 

 group 18 seeds were used for this exi^eriment tuid the rest for Experi- 

 ment IV. The field used was one of the College of xigriculture. Imperial 

 University, Tokyo, The soil of the field consisted of humus, aud the former 

 crop was AracMs liypocfaea L. The irnuliated seeds were sown with the 

 conti'ols and exti"a seeds, as in tlie former case, and 3 gi". of calciiuu sujier- 

 phospliate and ca. 100 gr. of stalile maniu-e were previously given. The 

 expeiiment extended fi'om April 1 to Juno 16 in 1917. 



Ihe results of this exi^erimeut are tibuhitad in Table III, and shown 

 in Textlig. 1 and Figs. 3-5. 



As the table and figures shu\\', the 20H-plants developed better in the 

 field than the conti'ols aud other iiradiated plants, «ud ths 40H-i>lauts ranted 

 next to the 20 H. 16 of 18 seeds of the 20 H aud 30 H germinated and 

 grew, aud the othca- invidiated sesds decreased iu the number of gprmimitions 

 proportional to the increase of the dose. None of the 155 H sprouted, but 

 they germinated under the ground aud develo^ied to the state shown in Fig. 6. 



Tlio dry weight of the plaaits, whose giw\th in tlie field was lietter, was 

 heavier tkm that of the othei«, as Table 3 shows (refer io the cm-ve). 



The experimental pl-mts were att:icked by Pipislrilhis ahramus since the 

 middlj of Ma}', aaid there were plants which became im^^eded in growth and 

 died, aud, moreover, they were so severely iujiu-ed that the floweis died Ix^foro 

 bearing fi'uits. This damage may have been caused by the unsuitable time 



