174 



EXPOSED WATER AND FRESHLY FALLEN RAIN 



May 29, 12 M. (Eighteen hours' growth.) 



Rain 

 10.00 mm. 

 11.00 

 (7.00) * 

 11.00 



33.00 mm. 

 10.67 rn"fi' 



Distilled 

 15.00 mm. 

 10.50 

 14.00 

 12.00 



51.50 mm. 

 12.88 mm. 



The difference of 2.22 mm. in favor of the roots grown in the 

 distilled water may have been lessened by the possible toxicity of the 

 latter, for it was not prepared in a glass still. Error from this cause 

 was eliminated in the next Experiment (No. 53). The figures for 

 the second day are omitted. (See figure 42.) 



Days 

 Fig. 42. Effect of freshly fallen Rain on the growth of Roots of Luphius albus. 



Experiment 53 



In this experiment, rain-water was caught in chemically clean 

 glass dishes in the open, on April 8, after about four hours of rain, 

 and again on May 7, after over three hours' precipitation. The ex- 

 periment was set up immediately after the last collection, using radi- 

 cles of Lu^inus albus, immersed in both the fresh and the stale rain- 

 water to a depth of 5 mm. Two parallel cultures, A and B, in both 

 the fresh and the stale rain-water were observed. The measured 

 lengths of the radicles, in millimeters, are given in the following 

 tables : 



* Discarded. 



