-e 
STIMULATION ON TURUESCENT VEGETABLE TISSUES. 3 
_ the horizon. This disturbance was not found in practice to 
interfere with the “ growth ’’* of the pith. 
The long arm of the lever ends in a needle-point, so that the 
- rate of its descent could be read off on a vertical scale divided 
- in millimeters. 
It was found that the best way of estimating variations in the 
rate of “ growth " was to record the times which the end of the 
lever occupied in travelling over a fixed vertical distance. A space 
of 1, 2, or 5 millim. was taken, and the movement of the needle- 
point was timed by means of a stop-watch. By taking the reci- 
procals of the stop-watch readings, a series of figures propor- 
7 tional to the rate of increase of the pith at short intervals of 
| time was obtained. And if the reciprocals are multiplied by 
1000, a convenient series of whole numbers are obtained, such as 
© we give in our Tables. Where the rate of growth, or more 
- briefly the “ rate,” is put down as 100, it means that the pith 
- was increasing in length at the rate of about half a millimeter 
- (046 millim.) per minute. Thus the unit of rate employed in our 
Tables is 00046 millim. of actual increase per minute. 
EXPERIMENTS. 
Before we describe the behaviour of the pith to reagents, we 
must consider its normal behaviour when placed in water. To 
give a general idea of the amount of increase in length which 
takes place in a short time, the following measurements are 
given :— 
Aug. 13, 1886.—Sunflower-pith increased in 1 hour 7 minutes 
at a temperature 17? C. from 192 millim. to 215 millim. 
Increase —23 millim., or 11:9 per cent. 
Aug. 13, 1886.—Jerusalem-Artichoke pith increased in 1 hour 
48 minutes at 16? C. from 215 millim. to 250 millim. 
Increase=35 millim., or 16:2 per cent. 
Apparent Grand Period. 
If the increase in length in water is studied by means of the 
auxanometer, it is found that the rate is at first slow, but gra- 
dually increases, and ultimately diminishes again, thus simulating 
* For the sake of brevity, we shall use the term “growth” to mean the 
increase in length of the pith. 
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