January 7, 1898.] 



SCIENCE. 



11 



at the close of two hours, when they stood 

 at an angle of 60°. He concludes from his 

 experiments that the Rontgen rays have 

 no taxic influence on seedlings. 



Experiment 8. Three species of Mucor 

 were sown in dilution cultures in nutrient 

 agar-agar, in Petrie dishes. After the 

 spores had begun to germinate one culture 

 of each was placed within 25 cm. of the 

 bulb, and the rays were then intercepted 

 from one-half of each culture by a piece of 

 sheet lead. A duplicate set of the cultures 

 was placed out of reach of the rays. The 

 cultures were exposed for four hours, and 

 returned to the culture room. No differ- 

 ence in growth was perceptible, the Ront- 

 gen rays neither inhibiting nor hastening 

 growth. 



Experiment 9. Several forms of chromo- 

 genic bacteria were then subject to the in- 

 fluence of the rays. Several tube cultures 

 in nutrient agar-agar were placed within 

 10 cm. of the bulb for about four hours. A 

 duplicate set was kept in the same house, 

 but outside of the field covered by the 

 Rontgen rays. From each of the two sets 

 of cultures inoculations were made into 

 fresh nutrient media. There was no per- 

 ceptible difference in growth nor in the 

 color as a result of the exposure to the rays. 



Experiment 10. A motile bacillus, B. 

 communis, was next placed within 15 cm. 

 of the bulb. The cultures were made in 

 bouillon and poured into Petrie dishes. 

 Two Petrie dish cultures were employed, 

 and the rays were intercepted from one- 

 half of each by sheet lead. They were ex- 

 posed six hours. From each half of the 

 two cultures then one drop was carried 

 to the third dilution, and four cultures 

 were then made from each of the second 

 and third dilutions in nutrient agar, and 

 distributed in Petrie dishes in order to com- 

 pare the number of colonies. The results 

 showed no difference in the proportionate 

 number of bacilli in the two halves of the 



Petrie dishes. The rays, therefore, have no 

 influence on the distribution of the bacilli 

 in the liquid, nor on their vitality for the 

 length of time exposed, a fact which Pro- 

 fessor Marshall- Ward had already demon- 

 strated. 



Experiment 11. A species of motile Oscil- 

 latoria was distributed in six watch glasses 

 with a small amount of water, the threads 

 being arranged in a tangled mass in the 

 center. Two of these were placed within 

 8 cm. of the bulb, two others at a distance 

 of 20 cm. with the Rontgen rays inter- 

 cepted by sheet lead, and the other two 

 placed outside of the dark room. The ex- 

 periment began at 12:30 p. m. and was dis- 

 continued at 4:30 p. m. In all the vessels 

 during this period of four hours the threads 

 moved out in a radiating fashion from the 

 centeir, and some had moved partly up the 

 sides of the vessels. In one of those ex- 

 posed to the influence of the rays the thread 

 had moved farther than in any of the 

 others, while in the other five vessels no 

 difference in the extent of the movement 

 was observed, and the greater movement 

 of the threads in one of the two exposed to 

 the rays could probably be accounted for 

 on other grounds. 



Experiment 12. The influence of the rays 

 was next tested on sensitive plants, Mimosa 

 piidica, grown in pots. Two plants were 

 used, and both were jarred, so that the 

 leaves dropped on their petioles and the 

 leaflets closed in pairs. The larger one, a, 

 was placed so that the nearest leaves were 

 within 10 cm. of the bulb after the dark 

 room had been dispensed with. The 

 smaller one was placed in another portion 

 of the same house, but where the daylight 

 was of the same intensity, so far as the eye 

 could judge. In twenty minutes the leaves 

 of the two plants had opened somewhat, 

 but b had opened more than a, which was 

 within the field of the rays. The plants 

 were then jarred a second time, and inter- 



