{18} See Dr. H. de Vries (ibid. p. 324) on this subject. {19} Comptes Rendus, 1844, tom. xix. p. 295, and Annales des Sc. Nat 3rd series, Bot., tom. ii. p. 163. {24} I am much indebted to Dr. Hooker for having sent me many plants from Kew; and to Mr. Veitch, of the Royal Exotic Nursery, for having generously given me a collection of fine specimens of climbing plants. Professor Asa Gray, Prof. Oliver, and Dr. Hooker have afforded me, as on many previous occasions, much information and many references. {33} Journal of the Linn. Soc. (Bot.) vol. ix. p. 344. I shall have occasion often to quote this interesting paper, in which he corrects or confirms various statements made by me. {34} I raised nine plants of the hybrid _Loasa Herbertii_, and six of these also reversed their spire in ascending a support. {36} In another genus, namely Davilla, belonging to the same family with Hibbertia, Fritz Müller says (ibid. p. 349) that “the stem twines indifferently from left to right, or from right to left; and I once saw a shoot which ascended a tree about five inches in diameter, reverse its course in the same manner as so frequently occurs with Loasa.” {37} Fritz Müller states (ibid. p. 349) that he saw on one occasion in the forests of South Brazil a trunk about five feet in circumference spirally ascended by a plant, apparently belonging to the Menispermaceæ. He adds in his letter to me that most of the climbing plants which there ascend thick trees, are root-climbers; some being tendril-bearers. {44} Fritz Müller has published some interesting facts and views on the structure of the wood of climbing plants in ‘Bot. Zeitung,’ 1866, pp. 57, 66. {68} It appears from A. Kerner’s interesting observations, that the flower-peduncles of a large number of plants are irritable, and bend when they are rubbed or shaken: Die Schutzmittel des Pollens, 1873, p. 34. {71} I have already referred to the case of the twining stem of Cuscuta, which, according to H. de Vries (ibid. p. 322) is sensitive to a touch like a tendril. {75} Dr. Maxwell Masters informs me that in almost all petioles which are cylindrical, such as those bearing peltate leaves, the woody vessels form a closed ring; semilunar bands of vessels being confined to petioles which are channelled along their upper surfaces. In accordance with this statement, it may be observed that the enlarged and clasped petiole of the _Solanum_, with its closed ring of woody vessels, has become more cylindrical than it was in its original unclasped condition.