{165} See M. Isid. Léon in Bull. Soc. Bot. de France, tom. v. 1858, p. 650. Dr. H. de Vries points out (p. 306) that I have overlooked, in the first edition of this essay, the following sentence by Mohl: “After a tendril has caught a support, it begins in some days to wind into a spire, which, since the tendril is made fast at both extremities, must of necessity be in some places to the right, in others to the left.” But I am not surprised that this brief sentence, without any further explanation did not attract my attention. {176} Sachs, however (‘Text-Book of Botany,’ Eng. Translation, 1875, p. 280), has shown that which I overlooked, namely, that the tendrils of different species are adapted to clasp supports of different thicknesses. He further shows that after a tendril has clasped a support it subsequently tightens its hold. {179} Annales des Sc. Nat. Bot. 4th series, tom. xii. p. 89. {180} It occurred to me that the movement of notation and that from a touch might be differently affected by anæsthetics, in the same manner as Paul Bert has shown to be the case with the sleep-movements of Mimosa and those from a touch. I tried the common pea and _Passiflora gracilis_, but I succeeded only in observing that both movements were unaffected by exposure for 1½ hrs. to a rather large dose of sulphuric ether. In this respect they present a wonderful contrast with Drosera, owing no doubt to the presence of absorbent glands in the latter plant. {181} Text-Book of Botany, 1875, p. 779. {183} Journal of Linn. Soc. vol. ix. p. 348. Professor G. Jaeger has well remarked (‘In Sachen Darwin’s, insbesondere contra Wigand,’ 1874, p. 106) that it is highly characteristic of climbing plants to produce thin, elongated, and flexible stems. He further remarks that plants growing beneath other and taller species or trees, are naturally those which would be developed into climbers; anti such plants, from stretching towards the light, and from not being much agitated by the wind, tend to produce long, thin and flexible shoots. {184} Professor Asa Gray has explained, as it would appear, this difficulty in his review (American Journal of Science, vol. xl. Sept. 1865, p. 282) of the present work. He has observed that the strong summer shoots of the Michigan rose (_Rosa setigera_) are strongly disposed to push into dark crevices and away from the light, so that they would be almost sure to place themselves under a trellis. He adds that the lateral shoots, made on the following spring emerged from the trellis as they sought the light. {187} Mr. Spiller has recently shown (Chemical Society, Feb. 16, 1865), in a paper on the oxidation of india-rubber or caoutchouc, that this substance, when exposed in a fine state of division to the air, gradually becomes converted into brittle, resinous matter, very similar to shell-lac.