BETWEEN GEOTROPISM AND GROWTH, 223 
Experiment IV.—Eight roots were marked at 2 millim.,5 millim., 
and 8 millim. from the tip, thus giving two spaces each of about 
3 millim. in length, for measurement. They were, as before, laid 
on damp peat after being operated on. 
The following table gives the results of measuring the 3-millim. 
space furthest from the tip of the root, i. e. between the 5 millim. 
and 8 millim. marks. 
Cut Roots. 
Lengths of Percentage Percentage 
measured growth in growth in 
space. 3 hours. 3 more hours. 
millim 
Pin 27 23 35 
rere ee 26 15 28 
BR 2... 27 11 27 
n ere 28 12 32 
Average...... 153 30:5 
Normal Roots. 
ee Ee 26 17 3 
Bs sm ve 2-7 37 24 
LR 26 14 33 
P eacus 30 31 33 
Average ...... 24:8 30 (leaving outi.*). 
The ratio between the average percentage growths are as 
follows :— 
First period :— 
eut : normal :: 100 : 162. 
Second period :— 
eut : normal : : 100 : 98. 
This experiment shows again how transitory is the effect of the 
operation, since during the second 3 hours the growth of the cut 
roots was slightly greater than that of the uncut roots. Yet the 
normal roots were all markedly geotropic, while the cut roots 
showed no curvature. The following table gives the results of 
measuring the apical space between 2 and 5 millim. from the tip 
in the same roots as those just given. 
* No. i. of the normal roots was excluded from the average of the third 
column because it had grown so little in the last period. 
