10 



SCIENCE. 



[N. S. Vol. VII. No. 158, 



those which had attained some growth be- 

 fore the beginning of the experiment was 

 also etiolated, the shoots being slender and 

 the leaves small. The leaves, which were 

 green at the start, gradually became nearly 

 or quite yellow. The wheat, oat and millet 

 seedlings were so weak that they fell pros- 

 trate, lying in all directions. At times it 

 appeared as if the rays might have some 

 peculiar taxic influence, since some of the 

 seedlings were turned, now in one direc- 

 tion and at a later time in another, but 

 there was no constancy in any of these 

 movements, and they were ascribed to nu- 

 tation. In fact, seedling plants which were 

 in the path of the Eontgen rays for a period 

 of over forty-five hours during five days did 

 not at the close of the experiment appear 

 in the least different from those in the same 

 dark room, but which were out of the reach 

 of the rays, and there was no appreciable 

 difference in behavior during the continu- ■ 

 ance of the experiment. 



That the seedlings were susceptible to 

 directive influences of ordinary daylight 

 was shown by their behavior when the 

 dark compartment was opened. At one 

 time the compartment was opened by part- 

 ing two of the hanging dark curtains for 

 about two minutes. Two hours afterward, 

 when the compartment was again opened, 

 nearly all the plants were turned strongly 

 toward this point. This appears to me to 

 be an interesting illustration of the great 

 sensitiveness of these etiolated plants to 

 light, and proves the fact that the response 

 to the stimulus occurs some time subse- 

 quent to the stimulus. 



The plants used in this experiment were 

 now placed in normal light, and were ob- 

 served carefully for several days. All of 

 the etiolated plants gradually became 

 green, but it was noticeable that those 

 which were not under the influence of the 

 Eontgen rays recovered more rapidly, 

 though the difference was not very striking. 



This suggests that there may be some sub- 

 tle injurious influence on the chloroplastids 

 of the plant. 



Experiment 7. The next experiment was 

 started on June 14th, at 9 a. m. The dark 

 cloth had been removed for the purpose of 

 growing seedlings under the Eontgen rays 

 which were at the same time exposed to 

 normal daylight. The seedlings were ar- 

 ranged in front of the bulb in the same way 

 as described for experiment 6. The follow- 

 ing seedlings were used : squash, wheat, oats, 

 pea, vetch, cow pea {Dolichos), sunflower,, 

 radish, soja bean, nonpareil bean and cot- 

 ton. The seeds were planted a few days in 

 advance, so that they were just coming 

 through the ground in various stages when 

 the experiment was started. A run of 

 fourteen hours was made on June 14th, and 

 of nine hours on June 15th, when this experi- 

 ment terminated. N"o influence whatever 

 from the Eontgen rays was observed. 



In 1896 Schober* published the results of 

 some experiments with the Eontgen rays 

 on seedlings ; these were undertaken for the 

 purpose of determining if short exposures 

 to the rays would produce taxic movements 

 in the nature of curving or bending of the 

 seedlings. Young oat seedlings were used 

 which had been germinated in a dark room, 

 and they were enclosed in a small geotropic 

 chest, blackened both on the inner and 

 outer side. This was so placed that they 

 were at a distance of two cm. from the 

 bulb at the opening of the chest. They 

 were exposed for one half hour, and after a 

 short interruption for another half hour. 

 No turning had taken place. In order to 

 see if the seedlings were sensitive to the 

 light they were then placed near a small- 

 opening in the side of the room, and in the 

 course of an hour perceptible heliotropic 

 movements began, which were more marked 



*Scliober, A. Ein Versuch mit Eontgen'schen 

 Strahlen auf Keimpflanzen. Ber. d. deutscli. Bot 

 Gesell. XIV., 108-110, 1896. 



