BETWEEN GEOTROPISM AND GROWTH. 225 
Normal Roots. 
Percentage 
ol Percentage ^ Percentage Percentage growth in 
Origins growth in growthin3 growthin3 21h. 40m. 
8 3 hours. more hours. more hours. from the 
millim. beginning. 
DEE 2:6 6 10 36 8 
H O... 2:6 7 7 15 143 
BE ses 27 11 . 28 23 196 
Average ...... 8 13:8 247 182:8 
The ratios between the averages in the four columns are :— 
After 3 hours. 3 more hours. 3 more hours. Whole growth. 
Normal roots ... 100 100 100 100 
Cut roots ......... 25 86 97 97 
Or, if we include “ cut ” root no. iii., 
Cüt roots... 25 70 70 86 
As all the roots were grown vertically, we have no knowledge 
of the geotropic curvature ; but there can be little doubt that the 
roots whose growth is given in the first of the two above tables 
would have shown no geotropism, whereas the normal roots would 
probably have shown clear geotropism. It will be seen that the 
operation only produced a severe effect for 3 hours, and that after 
6 hours the growth of the two sets of roots was practically equal. 
Experiment VI.—In the following experiment the roots were, 
as in the last case, grown vertically in damp air. They were 
measured by means of a microscope sliding horizontally and having 
cross wires in the eyepiece ; the lateral displacements were read 
off to O1 millim. by a vernier. The measured space was between 
2 and 10 millim. from the apex; 1:5 millim. was cut off 3 of the 
roots. 
Cut Roots. 
Percentage 
Ss Percentage Percentage growth from 
Original iel growth in 193 the beginning, 
lengths. 4 hours. hours additional. i.e. in 
millim. S 233 hours, 
Lo ow T4 14 152 187 
1 us. T6 11 96 117 
Hc el 7:6 12 101 125 
Average ...... 123 1163 143 
Normal Roots. 
i uos 74 16 103 137 
1h 4. 7-5 24 94 140 
Hi 78 13 65 86 
