Page:Researches on Irritability of Plants.djvu/139

116 .01 second. It will be seen that the responsive movement begins to occur between the tenth and eleventh dots, and very near the latter. There are thus 10.9 spaces, each of the value of .01 second, and the latent period is therefore .109 second. In order to test to what extent successive experiments might give concordant results, I took a second record with the same specimen, which appears in fig. 67 as the lower of the two, having given the plant an interval of rest of 20 minutes after the taking of the first record. It will be seen that the second record is essentially a replica of the first, thus demonstrating that with proper precautions

successive experiments on the value of the latent period will give results which are of extraordinary constancy.

By making the travel of the recording-plate very rapid, the successive dots become more widely spaced and the minute time-intervals involved are made more conspicuous. But this has the disadvantage of rendering the flexure of the curve representing the responsive movement less abrupt, making the exact point of initiation of response somewhat more difficult to discriminate. Going, on the other hand, to the opposite extreme of making the travel of the recording-plate slow, the flexure of the curve becomes more abrupt, enabling us the better to detect the point of initiation of the responsive movement. The time-dots, however, are now closer together. This can be seen in another record (fig. 68) obtained with a vigorous specimen. Here the