32 
Leitch. — Some Experiments on the Influence of 
3. Fall from high temperature to room temperature. 
Rate of growth given first for three half-hours, then in six-minute readings : 
Temperature. 27 0 , 27 0 , 27°, 27 0 , 25-5°, 21*2°, 20*3°, 20*2°, 20*0°, 19*8° = room temperature. 
Tate of growth. i-8 i-8 2*1 0*2 0-2 0*3 0-2 0*2 
4. Rise of temperature. 
Rate of growth given during first half-hour in six-minute readings, then in half-hour readings : 
Temperattire. 20*0°, 25*0°, 25*8°, 26*0°, 26-0°, 26*0°, 26-1°, 26*0° 
Rate of growth. 0-3 0-4 0*3 0*3 0-3 i-6 i-8 
5 - 
Temperature. 23*8 °, 26*5°, 27-0°, 27*0°, 27-0°, 27*0° 
Rate of growth. 0-3 0*3 0*3 0-2 0*3 
6 . 
Temperature. 23*9°, 26*1°, 26*5°, 26-6°, 26*6°, 26*6° 
Rate of growth. 0*4 0-3 0*3 0*4 0-3 
7. Finally the following experiment, where the results given are the 
means of measurements of eight peas : the rise of temperature is from 
room-temperature, about 18 0 to 25*2°. 
In the first, second, and third interval of ten minutes, the mean rate of 
growth was: 0-50, 0-475, °*475 1 that is, practically identical ; and the rates 
in the first and sixth half-hours were 1-45 and 1*45. 
From these experiments it will be clear that a change of temperature is, 
in itself, without effect ; but that the rate of growth follows immediately 
and accurately any considerable change of temperature. 
The next point to be considered is the possible effect on the experi- 
ments of the Grand Period of growth of the roots. In view of Sachs’s 
determinations, it appeared at first as if, in my experiments, taking place 
always at the beginning of the third day of growth, the slight rise to 
be expected during that day would be negligible, at least in short-period 
experiments. But in the long-period experiments at higher temperatures 
it had already become probable to me that Sachs’s results did not apply, and 
therefore, at the beginning of the microscope experiments, a series of 
determinations on the time of occurrence of the Grand Period was begun 
and continued intermittently. The roots were grown in long test-tubes with 
exactly the same other arrangements as in the microscope experiments, and 
measurements were made by applying a millimetre scale to the outside 
of the tube, a method which avoids all disturbances of growth by handling. 
Table II gives a full account of the results. Measurements were never 
continued after the appearance of the side-roots. 
