* 



23° 



THE POPULAR SCIENCE MONTHLY 



present in other portions of the leaf. The result was recorded by 

 exposing the leaf to sunlight in contact with the velox paper in a 

 printing frame. The region lacking starch, being more translucent, 

 gave the darkest image on the velox paper (Fig. 10). 



It was found possible to increase the rate of respiration of germi- 

 nating seeds by means of the rays, and alcoholic fermentation was also 

 accelerated by suitable exjaosure, as follows: Five fermentation tubes 



were filled with equal quantities of 

 a mixture of 2 gm. of a compressed 

 yeast cake in 250 c.c. of a 5 per 

 cent, solution of cane-sugar. Into 

 four of the fermentation tubes were 

 placed sealed glass tubes as follows : 

 IlaBr^ 1,500,000 X; 10,000 X; 

 7,000 X; radio-tellurium. The 

 fifth served as a control. At the 

 end of about three and one half 

 hours the cultures were photo- 

 graphed (Fig. 11). It is clearly 

 shown in the figure that the rate 

 of alcoholic fermentation, as measured by the evolution of gas, was 

 accelerated by the rays; most by the preparation of 1,500,000 activity, 

 least by that of 7,000 activity, and to an inteimediate degree by the 

 other preparations. 



Various attempts have been made to detect a tropistic response, or 

 curvature of a growing organ toward or from a radioactive source. 

 The phosphorescent light of radium has not been found intense enough 

 to call forth phototropic curvatures, and the existence of a true radio- 

 tropism is yet to be demonstrated. Koernicke found that seedlings 



Fig. 10. 



Fig. 11. 



