Chap. XVL] MOVEMENTS OF THE LEAVES. 303 



were a little unfolded to a greater degree in the younger than in 

 the older leaf. Tlie latter was not quite unfolded until the third 

 day, and now both bits of sponge were left at the distance of .1 of 

 an inch (2.54 mm.) from the edges; or about a quarter of the dis- 

 tance between the edge and the midrib. A third bit of sponge ad- 

 hered to the edge, and, as the margin unfolded, was dragged back- 

 wards, into its original position. 



Experiment 9. A chain of fibres of roast meat, as thin as 

 bristles and moistened with saliva, were placed down one whole 

 side, close to the narrow, naturally incurved edge of a leaf. In 3 

 hrs. this side was greatly incurved along its whole length, and after 

 8 hrs. formed a cylinder, about ^ijj of an inch (1.27 mm.) in di- 

 ameter, quite concealing the meat. This cylinder remained closed 

 for 32 hrs., but after 48 hrs. was half unfolded, and in 72 hrs. was 

 as open as the opposite margin where no meat had been placed. As 

 the thin fibres of meat were completely overlapped by the margin, 

 they were not pushed at all inwards, across the blade. 



Experiment 10. Six cabbage seeds, soaked for a night in water, 

 were placed in a row close to the narrow incurved edge of a leaf. 

 We shall hereafter see that these seeds yield soluble matter to 

 the glands. In 2 hrs. 25 m. the margin was decidedly inflected ; in 

 4 hrs. it extended over the seeds for about half their breatlth, and 

 in 7 hrs. over three-fourths of their breadth, forming a cylinder not 

 quite closed along the inner side. After 24 hrs. the inflection had 

 not increased, perhaps had decreased. The glands which had been 

 brought into contact with the upper surfaces of the seeds were now 

 secreting freely. In 36 hrs. from the time when the seeds were 

 put on the leaf the margin had greatly, and after 48 hrs. had com- 

 pletely, re-expanded. As the seeds were no longer held by the in- 

 flected margin, and as the secretion was beginning to fail, they 

 rolled some way down the marginal channel. 



Experiment 11. Fragments of glass were placed on the mar- 

 gins of two fine young leaves. After 2 hrs. 30 m. the margin of one 

 certainly became slightly incurved; but the inflection never in- 

 creased, and disappeared in 16 hrs. 30 m. from the time when the 

 fragments were first applied. With the second leaf there was a 

 trace of incurvation in 2 hrs. 15 m., which became decided in 4 hrs. 

 30 m., and still more strongly pronounced in 7 hrs., but after 19 

 hrs. 30 m. had plainly decreased. The fragments excited at most 

 a slight ana doubtful increase of the secretion; and in two other 

 trials, no increase could be perceived. Bits of coal-cinders, placed 

 on a leaf, produced no eflect, either owing to their lightness or to 

 the leaf being torpid. 



Experiment 12. We will now turn to fluids. A row of drops of 

 a strong infusion of raw meat were placed along the margins of two 

 leaves; squares of sponge soaked in the same infu.sion being placed 

 on the opposite margins. My object was to ascertain whether a 

 fluid would act as energetically as a substance yielding the same 

 soluble matter to the glands. No distinct difference was percep- 

 tible; certainly none in the degree of incurvation; but the incur- 

 vation round the bits of sponge lasted rather longer, as might per- 



