270 HIDEO KOIIDBO. 



on Jiine 16. Had he left the plants in the field, they would have been killed 

 by PipiäriUus, and an observation of the results wonld anyhow have become 

 impossible. He rooted up the plants, collected the fallen leaves of each plant, and 

 determined the dry weight of each group (dessicated by a water-bath and 

 dessicator), and intended to compare the dilTerences of eflect. 



One or two exceptionally stout seeds, M-hose iiradiation was above 80 H, 

 developed to a plant, but the majority did not sprout at all, aud no 155 H- 

 plants came out on the surface of the soil. The dose above 50 H seemed 

 to cause an injiu'ions stimulation for the S3eds whose water coutant was 50j'(^. 

 The IGO H-plaut died before the last oljservation. 



ExPEEiMENT r\^ 



This was the water culture by Knop's solution, but only two seeds for 

 each gi'oup were used for ti'ial, because of want of equipments. The principal 

 object of this experiment was to observe to what degree the plants will 

 develop, whose sprouts do not ap^sear above the sra'face of the soil. 



Two seeds of couti-ol, 20 H, 30 H, 40 H, 50 H, 69 H, 80 H, 100 H, 120 H 

 155 H were sown in a large pot containing siw-dust on April 2, 1917. The 

 seedlings of each group were brought into Knop's solution on April 9. Fig. 6 

 is the state on April 16, the 7th day after the treatment. 50 H-seedlings (for 

 the wouud) and seedlings above 80 H did not develop more than the state 

 shown in Fig. 6. Fig. 7 is a photogiviph taken on May 1, and Fig. 8 on 

 June 16 (at the end of the experiment). Tliese plants were placed in the 

 cold gi'eeu house of our Institute. On May 29, the writer foimd tlie parasite 

 of Bacilhm Fahae Uyeda on the leaves of tho 40 H-plant, so he pinched off 7 

 leaves. Afterwards, the plants of each gi'oup were attacked by PipistriUus 

 dbramus and 0.3_%' solution of " Katakilla " was often coated on with a brush. 



■\Vhen tho writer put the results of Experiments HI and V\ together, he 

 came to the conclusion that except the exceptionally stout mdividuals iiTadiated 

 material seems to havj Ijeen impeded in gi'owth generally at 60 H up, and 

 these plants ceased to gi'ow after a certain time. That is, these unspronted 

 ones germinated and devoloj^ed erpmlly for a certain period uudergi'oimd, and 

 even the seeds exposed to the raj'S of 155 H did not cease their development 

 at once but developed to a cei-tsiiu period as shown in Fig. 6. 



