effects on plant respiration 203 



Experiment 82 



Five seeds of the pea {Pisum sattvtini), soaked over night and 

 then freed of their seed-coats, were placed in a test-tube of mercury, 

 inverted in a bath of mercury. The weight of the seeds, minus the 

 seed-coats, was 2.29 gm. In the test-tube was first placed a sealed 

 glass tube of RaBrj (1,500,000 x ), with a cork over its upper end to 

 hold it at any desired level in the test-tube. Thus the seeds, when 

 placed into the test-tube, were aggregated about the lower end of 

 the radium-tube where the radium was, and so were brought closer 

 to the radium salt, and more directly under the influence of the rays. 



Control, with empty tube also supported by a cork, and with 

 seeds having a total weight of 2.28 gm. 



Observations of the amounts of gas given off by the seeds were 

 recorded as follows (see also figure 54) : 



Experiment 83 

 Four test-tubes were arranged as described in Experiment 82, the 

 total weight of the seeds (minus the seed-coats) in each case being 

 2.22 gm. The first three test-tubes contained radium preparations 

 as indicated in the following table. Observations of the volumes of 

 gas evolved in the test-tubes were recorded as follows : 



Radium Radium Radio- 



Time of Observation 1,500,000 X io,oooX tellurium Control 

 June I, 6 : 00 P. M. 0.00 c.c. 0.00 c.c. 0.00 c.c. 0.00 c.c. 



" 2, 10:00 A.M. .40 .60 .60 .60 



1. 10 



" 3, 1 1 : 00 A. M. .80 1.60 1.30 



" 4, i2:ooM. 1.35 1.30 1.25 1. 00 



" 5,12:15P.M. .97 1.20 1.25 1.20 



" 6, '11: 00 A.M. 1.63 1.65 1.50 1.35 



5.15 c.c. 6.35 c.c. 5.90 c.c. 5.25 c.c. 



