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Show 140 SENSITIVENESS OF TilE APEX CrrAP. III. (4.0.) Square of card gummed to apex: after 9 h. slightly cnrved from card; next morning radicle Rtra.ight, and apex had grown beyond the carcl. Refixecl another square bterally with shellac; in 9 h. deflected latemlly, but also in the direction of Sachs' curvature. After 2 ndditional days' curvature considernbly increased in the same direction. (41.) Little square of tin-foil fixed with gum to one side of apex of a young and short radicle: after 15 h. no effect, but tjn-foil hnd become displaced. A little square of card was now gummed to one side of apex, which after 8 h. 40 m. was slightly deflected; in 21 h. from the time of attachment deflected at 900 from the perpendicular and from the card; after 9 additional hours became hooked, with the apex pointing to the zenith. In 3 days from the time of attachment the terminal portion of tho radicle formed a ring or circle. (42.) A little square of thick letter-paper gummed to tho apex of a radicle, which after 9 h. was deflected from it. In 24 h. from time when the paper was affixed the deflection much increased, and after 2 additional clays it amounted to 50° fro:n the perpendicular and from the paper. (43.) A narrow chip of a quill was fixed with shellac to the apex of a radicle. After 9 h. no effect; after 24 b. moderate deflection, but now the quill had ceased to touch the apex. Removed quill and gummed a little square of card to apex, which after 8 h. caused slight deflection. On tho fourth day from the first attachment of any object, tho extreme tip was curved towards the card. (44.) A rather long and narrow splinter of extremely thin glass, fixed with shellac to apex, it caused in 9 h. slight deflection, which disappeared in 24 h.; the splinter was then found not touching the apex. It was twice refixed, with nearly similar results, that is, it caused slight deflection, which soon disappeared. On the fourth day from the time of first attachment the tip was bent towards tho splinter. From these experiments it is clear that the apex of the radicle of the bean is sensitive to contact, and that it causes the upper part to bend away from the touching ol>ject. But before giving a summary of the results, it will be convenient briefly to give a few other observations. Bits of very thin glass and little squares CHAP. III. OF THE RADICLE OF THE DEAN. 141 of common card were affixed with thick gum-water to the tips of the radicles of seven beans, as a preliminary trial. Six of these wore plainly acted on, and in two cases the radiclcs became coiled up into complete loops. One radicle was curved into a semicircle in so short a period as 6 h. 10 m. The s?venth ra?icle which was not a:fl'cctcd was apparently swkly, as It became brown on tho followin()" day · so that it formed no real exception. Some of those t;.ials were made in the early spring durin()" cold weather in • • b a s1ttmg-room, and others in a greenhouse, l>ut the temperature was .not recorded. These six striking cases almost convmccd us that the apex was sensitive, but of course we determined to make many more trials. As. we had noticed that the radiclcs grew much more qmckly when subjected to . considerable heat, and as we imagined that heat would increase th ir sensitiv - ness, v~ssels with germinating beans suspended in damp au. were pla?ed on a chimney-pi co, where they were subJected durmg the greater part of the clay to a temperature of between 69° and 72° F.; some, however, were placed. in the hot-house whore the temperature was rather higher. Above two dozen beans were thus tried; and when a square of glass or card did no~ act, it was removed, and a fresh one affixed, this bemg often done thrice to the same radicle. Therefore between five and six dozen trials were altogether made. But there was moderately distinct deflection ~rom the perpendicular and from tho attach d. object ~:only one radicle out of this large number of cases. d fl :five. other cases there was very slight and doubtful e ectwn · We wore as t om.s h e d at thi.s result and :~:l~ded that w~ had m~de some inexplicable' misrelin 1~ t~e first SIX expenments. But before finally qmshing the subject, we resolved to make one |