380 True. — On the Influence , of Sudden Changes of 
Passing to the experiments involving the use of the hori- 
zontal microscope, attention is first called to the normal 
growth as observed in control-experiments in water. 
In Table VIII are shown the increments of growth made by 
a root of Vicia Faba , as determined by half-hourly observa- 
tions. The total length of the root at the beginning of the 
experiment was 23 mm. Temperature, 20«o°-23-o° C. 
As was above suggested, if a root growing in sawdust be 
brought into water, a slight elongation is usually seen to occur, 
due to the swelling of the cell-membranes and to a slight 
increase of turgor-pressure in case the object was not already 
fully turgescent. This elongation is usually followed by a 
TABLE IX. 
Period. 
Growth. 
Medium. 
II-II.30 
1 6*o units of scale 
Water 
tu 
0 
to 
i7-o „ 
12-12.30 
3*5 » 
i%KN0 3 
12.30-1 
7*5 '>•> » 
... 
1-2.30 
*13-0 „ 
V 
2.30-3 
17*0 „ 
>> 
3-3*30 
23-0 „ 
>> 
3*30-4 
27-0 „ 
4-4*30 
45*0 „ 
Water 
4*30-5 
26*0 „ „ 
>> 
* Rate per half-hour. 1 unit of scale = 0*0169 mm. 
somewhat retarded rate of growth, arising probably as an 
irritative response to the changed conditions of water and of 
oxygen-supply. After an hour or two, the normal rate is 
generally restored. 
It may also be mentioned here that the transfer of a root 
from the sawdust to the observation vessel involves a great 
change in the conditions of illumination. Whether roots are 
in any considerable degree sensitive to sudden changes of this 
nature seems to be a question that has not yet received 
attention. 
In Table IX is shown the course of growth of a root of 
