The effect of cutting off with a razor a thin slice from one side of the conical apex of 14 young and short radicles was next tried.  Six of them after being operated on were suspended in damp air; the tips of the other eight, similarly suspended, were allowed to enter water at a temperature of about 65o F. It was recorded in each case which side of the apex had been sliced off, and when they were afterwards examined the direction of the curvature was noted, before the record was consulted.  Of the six radicles in damp air, three had their tips curved after an interval of 10 h. 15 m. directly away from the sliced surface, whilst the other three were not affected and remained straight; nevertheless, one of them after 13 additional hours became slightly curved from the sliced surface.  Of the eight radicles with their tips immersed in water, seven were plainly curved away from the sliced surfaces after 10 h. 15 m.; and with [page 167] respect to the eighth which remained quite straight, too thick a slice had been accidentally removed, so that it hardly formed a real exception to the general result.  When the seven radicles were looked at again, after an interval of 23 h. from the time of slicing, two had become distorted; four were deflected at an angle of about 70o from the perpendicular and from the cut surface; and one was deflected at nearly 90o, so that it projected almost horizontally, but with the extreme tip now beginning to bend downwards through the action of geotropism.  It is therefore manifest that a thin slice cut off one side of the conical apex, causes the upper growing part of the radicle of this Phaseolus to bend, through the transmitted effects of the irritation, away from the sliced surface.

Tropaeolum majus:  Sensitiveness of the apex of the Radicle to contact.—­ Little squares of card were attached with shellac to one side of the tips of 19 radicles, some of which were subjected to 78o F., and others to a much lower temperature.  Only 3 became plainly curved from the squares, 5 slightly, 4 doubtfully, and 7 not at all.  These seeds were, as we believed, old, so we procured a fresh lot, and now the results were widely different.  Twenty-three were tried in the same manner; five of the squares produced no effect, but three of these cases were no real exceptions, for in two of them the squares had slipped and were parallel to the apex, and in the third the shellac was in excess and had spread equally all round the apex.  One radicle was deflected only slightly from the perpendicular and from the card; whilst seventeen were plainly deflected.  The angles in several of these latter cases varied between 40o and 65o from the perpendicular; and in two of them it amounted after 15 h. or 16 h. to about 90o.  In one instance a loop [page 168] was nearly completed in 16 h.  There can, therefore, be no doubt that the apex is highly sensitive to slight contact, and that the upper part of the radicle bends away from the touching object.