1920] 



PHILLIPS— GEO TROPISM 



171 



nodes were exposed to gravity for varying lengths of time, from 

 3 to 27 hours. In the last column, + is in favor of the convex side 



and 



the 



This method of statement is used 



in all the tables. As already mentioned, corn nodes are not at all 

 uniform in their response to gravity, and because of this fact a 

 second set was run in which nodes that had bent approximately 

 to the degree indicated were used. The results will be found in 



table II. 



Moisture 



TABLE II 



ACIDITY IN CORN NODES EXPOSED TO GRAVITY 



Degree of 



BENDING 



Moisture 



Acidity in cc. 0.05 N NaOH 



PER GM. FRESH WEIGHT 



I 



o 



5 



5 



5 



10 



10 



IS 



20 



2 5 



2 5 



Upper flank 

 (percentage) 



82.41 

 80.27 

 81 .19 

 8468 

 80.42 

 86.04 

 86.31 



85 .13 

 87.12 



8752 



Lower flank 

 (percentage) 



81.30 

 80.08 

 80.44 

 84.21 



So. 77 



86.35 

 87.63 

 87.60 



89.52 



89.29 



Difference 

 (percentage) 



Upper flank 



I 



— I .II 



— o. 19 



-0.75 

 -0.47 



+0.35 

 +0.31 



+1.32 



+2.47 



+2.40 



+ I-77 



0.62 

 0.72 

 0.60 

 0.60 



o.75 

 0.56 



0.65 



0.66 



0.80 



0.66 



Lower flank 



0.65 



0-75 



0.73 

 0.63 



0.83 

 0.60 



0.72 



0.80 



0.76 



0.71 



Difference 



+003 

 +O.03 



+0.13 

 +O.03 



+O.08 



+0.04 



+O.07 



+O.14 

 —O.04 



+O.05 



Individual differences in moisture content are so great that 

 different samples cannot be compared. It is only possible to 

 compare opposite flanks of the same sample. In general the 

 differences are slight, and in view of the high percentage of moisture 

 present they may not be significant. There are some features of 

 the results which are of interest, however, especially when the two 

 sets are compared. In the time of exposure set the differences are 

 variable, but in general favor the convex side up to 9 hours of 

 exposure. At 12 and 15 hours, when bending is well started, there 

 is a decided difference in favor of the concave side. At 18, 2i t and 

 27 hours the convex side contains much more moisture. The results 

 at 24 hours appear to be anomalous, especially as no corresponding 



change is found in the other set. 



In the degree of bending set the 



& 



differences are more regular and more marked. During the early 

 stages of bending the concave flank contains the more moisture, but 



