show, which are given to prove that a touch with caustic on one side of the tip does not prevent the upper part of the radicle from bending.  Ten radicles were laid horizontally beneath and on damp friable peat, and their tips were touched with caustic on the upper side.  After 8 h. all were plainly geotropic, three of them rectangularly; after 19 h. [page 538] all were strongly geotropic, most of them pointing perpendicularly downwards.  Ten other radicles, similarly placed, had their tips touched with caustic on the lower side; after 8 h. three were slightly geotropic, but not nearly so much so as the least geotropic of the foregoing specimens; four remained horizontal; and three were curved upwards in opposition to geotropism.  After 19 h. the three which were slightly geotropic had become strongly so.  Of the four horizontal radicles, one alone showed a trace of geotropism; of the three up-curved radicles, one retained this curvature, and the other two had become horizontal.

The radicles of this plant, as already remarked, do not succeed well in damp air, but the result of one trial may be briefly given.  Nine young radicles between .3 and .5 inch in length, with their tips cauterised and blackened for a length never exceeding ½ mm., together with eight control specimens, were extended horizontally in damp air.  After an interval of only 4 h. 10 m. all the controls were slightly geotropic, whilst not one of the cauterised specimens exhibited a trace of this action.  After 8 h. 35 m., there was the same difference between the two sets, but rather more strongly marked.  By this time both sets had increased greatly in length.  The controls, however, never became much more curved downwards; and after 24 h. there was no great difference between the two sets in their degree of curvature.

Eight young radicles of nearly equal length (average .36 inch) were placed beneath and on peat-earth, and were exposed to a temp. of 75o — 76o F. Their tips had been touched transversely with caustic, and five of them were blackened for a length of about 0.5 mm., whilst the other three were only just visibly discoloured.  In the same box there were 15 control radicles, mostly about .36 inch in length, but some rather longer and older, and therefore less sensitive.  After 5 h., the 15 control radicles were all more or less geotropic:  after 9 h., eight of them were bent down beneath the horizon at various angles between 45o and 90o, the remaining seven being only slightly geotropic:  after 25 h. all were rectangularly geotropic.  The state of the eight cauterised radicles after the same intervals of time was as follows:  after 5 h. one alone was slightly geotropic, and this was one with the tip only a very little discoloured:  after 9 h. the one just mentioned was rectangularly geotropic, and two others were slightly so, and these were the three which had been scarcely [page 539] affected by the caustic; the other five were still strictly horizontal.  After 24 h. 40 m. the three