The radicles in the foregoing cases were measured before their tips were amputated, and in the course of 24 h. they had all increased greatly in length; but the measurements are not worth giving.  It is of more importance that Sachs found that the rate of growth of the different parts of radicles with amputated tips was the same as with unmutilated ones.  Altogether twenty-nine radicles were operated on in the manner above described, and of these only a few showed any geotropic curvature within 24 h.; whereas radicles with unmutilated tips always became, as already stated, much bent down in less than half of this time.  The part of the radicle which bends most lies at the distance of from 3 to 6 mm. from the tip, and as the bending part continues to grow after the operation, there does not seem any reason why it should not have been acted on by geotropism, unless its curvature depended on some influence transmitted from the tip.  And we have clear evidence of such transmission in Ciesielski’s experiments, which we repeated and extended in the following manner.

Beans were embedded in friable peat with the hilum downwards, and after their radicles had grown perpendicularly down for a length of from ½ to 1 inch, sixteen were selected which [page 526] were perfectly straight, and these were placed horizontally on the peat, being covered by a thin layer of it.  They were thus left for an average period of 1 h. 37 m.  The tips were then cut off transversely for a length of 1.5 mm., and immediately afterwards they were embedded vertically in the peat.  In this position geotropism would not tend to induce any curvature, but if some influence had already been transmitted from the tip to the part which bends most, we might expect that this part would become curved in the direction in which geotropism had previously acted; for it should be noted that these radicles being now destitute of their sensitive tips, would not be prevented by geotropism from curving in any direction.  The result was that of the sixteen vertically embedded radicles, four continued for several days to grow straight downwards, whilst twelve became more or less bowed laterally.  In two of the twelve, a trace of curvature was perceptible in 3 h. 30 m., counting from the time when they had first been laid horizontally; and all twelve were plainly bowed in 6 h., and still more plainly in 9 h.  In every one of them the curvature was directed towards the side which had been downwards whilst the radicles remained horizontal.  The curvature extended for a length of from 5 to, in one instance, 8 mm., measured from the cut-off end.  Of the twelve bowed radicles five became permanently bent into a right angle; the other seven were at first much less bent, and their curvature generally decreased after 24 h., but did not wholly disappear.  This decrease of curvature would naturally follow, if an exposure of only 1 h. 37 m. to geotropism, served to modify the turgescence of the cells, but not their subsequent