EFFECTS ON THE SYNTHESIS OF CARBOHYDRATES I93 



After an exposure for 8 hours, the leaves were tested for starch. 

 Starch was found in all the leaves, but there was decidedly more 

 starch apparent in those floated on the control solution, than in those 

 floated on the solution exposed to the rays of radium. 



Whatever effect the rays may have had on the solution per- 

 sisted for at least two days, and resulted in a retardation of starch- 

 making by the plastids. 



3. Effect on Chlorophyll Solution and Chloro- 

 phyll Paste 



Experiment 74 



Object : To ascertain the effect of the rays of radium on an alco- 

 holic solution of chlorophyll. 



An alcoholic solution of chlorophyll was prepared by soaking 

 filaments of Spirogyra in cold 95 per cent, alcohol. The solution 

 was then filtered and divided into two halves. Into one was sus- 

 pended a sealed glass tube containing 10 mg. of RaBr2 of 1,500, 

 000 activity, with the end containing the radium in about the middle 

 of the solution. In the other was placed nothing. Both vials were 

 set in the dark-room, at the same temperature. 



Frequent observations during a period of 89 hours disclosed no 

 appreciable difference in the appearance of the two solutions. The 

 radium-tube was then removed, and the solutions left to stand in the 

 dark-room for eight weeks. At the end of that time there was no 

 difference in their appearance, and when both vials were then placed 

 in the sunlight the solutions behaved precisely alike, so far as could 

 be detected, while they were bleaching. 



Repetitions of this experiment were followed by similar (negative) 

 results. In the second and third experiments the solutions were 

 made respectively from leaves of nasturtium {Tropaeohuii) and bean 

 {Phaseolus). 



Experiment 75 



A small box with a mica window, and containing 10 mg. of 

 RaBr, of 1,800,000 activity, was placed over a small bit of chloro- 

 phyll paste (" Chlorophyll Puriss.,"of supply houses), with only the 

 mica between the radium and the paste. The exposure was made 

 in the dark-room for 18 hours, but no visible effect from the radium 

 resulted to the chlorophyll. 

 14 



