PLANT-AUTOGRAPHS—BOSE. 433 
ing to make such measurements the results are vitiated by our 
personal limitations. The conditions of the experiment demand 
accurate measurements of time-intervals shorter than a hundredth 
part of a second; but sluggishness of our perception makes such an 
attempt an impossibility. It is therefore absolutely necessary to 
invent a special device by which the plant itself should be compelled 
to write down its own latent period. In the case of the leg muscle 
of a frog the latent period, according to Helmholtz, is about a 
hundredth part of a second. This result is not without some error, 
on account of the inertia of the recording lever, and the inferring of 
time relations from a neighboring chronographic record. In my 
resonant recorder these errors have been reduced to a minimum. 
In the first place, the curve of response or phytogram is at the same 
time a chronogram. Secondly, the weight of my plant recorder is 
only a hundredth part of the usual muscle recorder. The latent 
period of the animal tissue undergoes appropriate variation with 
Fig. 11.—Record showing. the latent period of Mimosa. This recorder vibrates 200 times per 
second. The time-interval between successive dots is here 0.005 sec. 
changing external conditions. With feeble stimulus it has a definite 
value; this becomes shortened under a stronger blow. Again, when 
we are tired our perception time becomes prolonged. Every one of 
these results is equally applicable in the case of the plant. The 
delicacy of the resonant recorder will be understood from the response 
curve exhibiting the latent period of Mimosa (fig. 11). Here deter- 
mination is carried to a thousandth part of a second, the value being 
0.076 seconds, or eight times its value in an energetic frog. The 
reliability of this method can be gauged from successive records under 
uniform conditions, when the results are found to be identical. 
Another curious thing is that a stoutish plant will give its response 
in a slow and lordly fashion, whereas a thin one attains the acme of 
its excitement in an incredibly short time. Perhaps some of us can 
tell from our own experience whether similar differences obtain 
among human kind. The perception time of the plant becomes 
73176°—sM 191428 
