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Show 168 SENSITIVENESS OF TilE APEX CHAP. III. was nearly completed in 16 h. There can, therefore, be no doubt that the apex is highly sensitive t o slight contact, and that the upper part of tho radicle bends away from the touching object. Gossypium herbaceum: Sensitiveness of the apex of the Radicle.-Radicles were exp rimonted on in tho same manner as before, but th y proved ill-fitted for our purpose, as they soon became unhealthy when suspended in damp air. Of 38 radicles thus suspended, at t emperatures varying from 66° to 69° F., with squares of card attached to their tips, 9 were plainly and 7 slightly or even doubtfully deflected from the squares and from the perpendi ·ula.r; 22 not being affected. We thought that perhaps tho above temperature was not high enough, so 19 ra<liclos with attached squares, likewise suspended in damp air, were subj ected to a temperature of from 74° to 79° F., but not one of them was acted on, and they soon became unhealthy. Lastly, 19 radicles were suspended in water at a temperature from 70° to 75° F., with bits of glass or squares of tho card attached to their tips by metms of Canada-balsam or asphalte, which adhered rather better than shellac beneath the water. Tho radiclos did not keep healthy for long. Tho result was that 6 were plainly and 2 doubtfully defl ctod from the attached objects and the perpendicular; 11 not being affected. The evidence consequently is hardly conclusive, though from the two sets of cases tried und~r a moderate temperature, it is probable that the rachcles are sensitive to contact· and would be more so under ' favourable conditions. Fifteen radicles which had germinated in friable peat were suspended vertically over water. Seven of t~em served as controls, and they remained quite stra.Ight during 24 h. The tips of the other eight radiCles CrrAP. III. OF TILE RADICLE OF CUCURDI'l'A. 1t1D were just touched with dry caustic on one sjcle. After only 5 h. 10 m. five of them were slightly curved from the perpendicular and from tho sifle b aring the little blackish marks. Aft r 8 h. 40 m., 4 out of these 5 were deflected at angl s betw en 15° and 65° from the perpendicular. On the other hand, one which had been slightly curved after 5 h. 10 m., now became straight. After 24 h. tho curvature in two cases had considerably increased; al so in four other cases, but these latter radiclos had now become so contorted, some being turned upward , tl1at it could no longer be ascertained whether they wore still curv c1 from the cauterised side. The control p cimens exhibited no such irregular growth, and the two sets presented a striking contrast. Out of tho 8 radicles which had been touched with caustic, two alone wore not affected, and tho marks left on their tips by the caustic were extremely minute. Th so marks in all cases were oval or elongated; th y were m a urecl in three instances, and found to be of nearly the same size, viz.~- of a mm. in length. Bearing this fact in mind, it should be observed that the l ngth of the curved part of the radicle, which had become defl.octocl from the cauterised side in the course of 8 h. 40 m., was found to be in three cases 6, 7, and 9 mm. . Cucurbita ovifera : Sensitiveness of the apex of the Rad~ cle.-The tips proved ill-fitted for the attachment of cards, as they are extremely :fine and flexible. l\Ioreover, owing to the hypocotyls beino· soon developed ~~d becoming arched, the whole r~dicle is quickly Isplaced and confusion is thus caused. A large number of trials were made, but without any definite result, excepting on two occasions when out of 23 ra d I' C1e s 10 were deflected from tho' attached squares |