8o MOVEMENTS OF CURVATURE 



Our knowledge as to how the movement of the pulvinus of Mimosa pudica is 

 produced by the antagonism of the upper and under halves has developed gradually l , 

 Lindsay in 1790 considered the fall of the petiole to be due to the expansion of the 

 upper half of the pulvinus, whereas Burnett and Mayo 2 recognized that only the 

 under half of the pulvinus of Mimosa is irritable, but failed to gain a correct view of 

 the entire mechanism. After Dutrochet, Treviranus and Mohl had collected definite 

 facts in regard to the strains between the distended parenchyma and the vascular 

 bundles, Briicke definitely established the fact that the curvature is the result of 

 the under half of the pulvinus becoming flaccid 3 . 



The varying grades of irritability in the leaves of Mimoseae, Papilionaceae, and 

 Oxalidaceae have already been discussed 4 . Meyen 5 observed that the leaves of 

 Gleditschia iriacantha possessed a feeble seismonic irritability, and Mohl 6 observed 

 the same in the leaves of Robinia pseudacada, R. viscosa, and R. hispida. In many 

 cases even the cotyledons are irritable, as was shown by A. P. de Candolle 7 in the 

 case of Mimosa pudica, and by Darwin 8 in those of Oxalis sensitiva, Smithia sensitiva, 

 and a few species of the genus Cassia, Dionaea, and Aldrovanda. When the leaf of 

 Dionaea muscipula is stimulated the two halves of the leaf fold sharply together and 

 become at the 'same time somewhat concave, so that the marginal teeth interlock 9 

 (cf. Fig. 57, p. 378, Vol. i). Apart from the marginal zone, the whole leaf seems to take 

 an active part in the movement. According to Batalin's measurements, the most pro- 

 nounced curvature takes place along a zone on each side parallel to the midrib, while 

 the midrib itself takes little or no part in the movement. Darwin 10 , however, found 

 that a pronounced movement occurs along the midrib. Batalin 11 considered the 

 movement to be mainly the result of growth, but it is not certain whether young and 

 old leaves behave alike in this respect. The observations and discussion of Darwin 

 and of Munk fail to definitely decide whether the movements of Dionaea are wholly 

 or partially due to a similar cell-mechanism as that which exists in the pulvinus of 

 Mimosa pudica. 



1 Pfeffer, Physiol. Unters., p. 3. 



2 Burnett and Mayo, Quarterly Journal of Science, Literature and Arts, 1827, Vol. XXIV, p. 79; 

 1828, Vol. xxv, p. 434. 



3 Cunningham (Annals of the Royal Botanical Garden of Calcutta, 1895, Vol. VI, p. i) goes so 

 far as to doubt whether the movements of Mimosa pudica are irritable movements at all, but this 

 somewhat voluminous work is without value. 



4 An enumeration of the sensitive plants is given by Hansgirg, Physiol. und phycophytolog. 

 Unters., 1893, p. 118; Neue Unters. iib. d. Gamo- und Karpotropismus, 1896, p. 102 (reprint from 

 Sitzungsb. d. bohm. Ges. d. Wiss.). Numerous cases were given by Dassen, in Wiegmann's Archiv 

 f. Naturgeschichte, 1838, Bd. I, p. 347 ; Meyen, Physiologic, 1839, Bd. ill, p. 539. 



5 Meyen, 1. c., p. 540. 6 Mohl, Vermischte Schriften, 1845, p. 372. 



7 A. P. de Candolle, Physiologic, a German translation by Roper, 1835, Bd. n, p. 647. 



8 Darwin, The Power of Movement in Plants. 9 Ibid. 



10 For details see Darwin, Insectivorous Plants ; Munk, Die elektrischen- und Bewegungs- 

 erscheinungen am Blatte von Dionaea muscipula, 1876, p. 97 ; Batalin, Flora, 1877, p. 105; Burdon- 

 Sanderson, Proceedings of the Royal Society, 1877, Vol. XXV, p. 411 ; Phil. Trans., 1882, p. 48 of 

 the reprint; Goebel, Pflanzenbiol. Schilderungen, 1891, n, p. 68; 1893, ir, p. 201; Macfarlane, 

 Contributions from the Biological Laboratory of Pennsylvania, 1892, Vol. I, p. 7; Biological 

 Lectures, 1894, p. 187. See more especially Haberlandt, Sinnesorgane im Pflanzenreich, 1901, 

 p. 108. u 1. c. 



