144 SENSITIVENESS OF THE APEX Chap. Ill, 



ments of very thin glass, &c., were affixed at different 

 fjmes to one side of the conical tips of 55 radicles. 

 The 11 last-mentioned cases, but not the preliminary 

 ones, are here included. The squares, &c., were most 

 commonly affixed with shellac, but in 19 cases with 

 thick gum-water. When the latter was used, the 

 squares were sometimes found, as previously stated, 

 to be separated from the apex by a layer of thick 

 fluid, so that there was no contact, and conse- 

 quently no bending of the radicle ; and such few 

 cases were not recorded. But in every instance in 

 which shellac was employed, unless the square fell 

 oif very soon, the result was recorded. In several 

 instances when the squares became displaced, so as 

 to stand parallel to the radicle, or were separated by 

 fluid from the apex, or soon fell off, fresh squares 

 were attached, and these eases (described under the 

 numbered paragraphs) are here included. Out of 

 55 radicles experimented on under the proper tempe- 

 rature, 52 became bent, generally to a considerable 

 extent from the perpendicular, and away from the 

 side to which the object was attached. Of the three 

 failures, one can be accounted for, as the radicle 

 became sickly on the following day; and a second 

 was observed only during 11 h. 30 m. As in several 

 cases the terminal growing part of the radicle continued 

 for some time to bend from the attached object, it 

 formed itself into a hook, with the apex pointing to 

 the zenith, or even into a ring, and occasionally into a 

 spire or helix. It is remarkable that these latter cases 

 occurred more frequently when objects were attached 

 with thick gum-water, which never became dry, than 

 when shellac was employed. The curvature was often 

 well-marked in from 7 h. to 11 h. ; and in one instance 

 a semicircle was formed in 6 h. 10 m. from the time 



