258 



DION^A MUSCIPULA. 



[Chap. XIII. 



Finally, with respect to the movement of the leaves the 

 wonderful discovery made by Dr. Burdon Sanderson " is now 

 universally known; namely that there exists a normal elec- 

 trical current in the blade and footstalk; and that when the 

 leaves are irritated, the current is disturbed in the same 

 manner as takes place during the contraction of the muscle 

 of an animal." 



place. It will be seen that Bata- 

 lln's observations do not support 

 the Idea (see p. 259) that the re- 

 opening of the loaf Is due to the 

 return of the outer cells to their 

 natural size when the tension put 

 on them by the contraction of 

 the Inner surface Is removed. 

 Munk (loc. cit.) and Pfoffer (' Os- 

 motlsche UntersuchunKon,' 1877, 

 p. IIMJ) have with Justice called 

 attention to the unsatisfactory 

 nature of the discussion In the 

 text on the mechanlsni of the 

 movement. Batalln shows fur- 

 ther that the ultimate closure? of 

 the leaf by which the two valves 

 are closely pressed together Is 

 effected by the shortening or 

 contraction of the outer surface 

 of the leaf. He records a curious 

 fact which has not elsewhere 

 been noted, namely, that the mid- 

 rib becomes more curved after 

 the closure of the leaf. Munk 

 (Uelchert and Du Bols-Ucyinoud's 

 ' Archlv.' 1870, p. 121). on the 

 other hand, Is Inclined to believe 

 that the curvature .of the midrib 

 diminishes when the leaf closes. 

 -F. I).] 



u ' proc. Royal Soc.' vol. xxl. 



f. 41>r>; and lecture at the Royal 

 nstltutlon. June .'>, 1874, given In 



Nature,' 1874. pp. 105 and 127. 



" [Professor Simflerson's work 

 has been crltlclHod by Professor 

 Munk In Relchert and Du Bots- 

 Reymond's ' Ar<-hlv.' 1870, and 

 by Professor Kunkel In Sachs' 



Arbelten a. d. Iwt. Instltut In 

 Wllntburg,' Bd. II. p. 1. 



Professor Sanderson has con- 

 tinued to work at the subject, 

 and has given his results In an 

 elaborate paper In ' Phil. Trans- 

 actions,' 1882. It will be suffi- 

 cient to note his conclusions with 

 regard to the two points men- 

 tioned In the text. First, for the 

 electrical condition of the leaf at 

 rest. Sanderson rejects Mtmk's 

 method of explaining the state 

 of the leaf by a mechanical 

 trhrmnnn arrangement of cop- 

 per and sine cylluderB. He does 



BO, not only because he accepts 

 " as fundamental the doctrine 

 that whatever physiological prop- 

 erties the leaf poHscHscs, It pos- 

 sesses by virtue of Its being a 

 system of living cells; " but also 

 because the facts of the case are 

 not In accordance with Professor 

 Munk's th(>oretlcal deductions. 

 He Inclines to admit that the 

 electrical differences observtHl be- 

 tween different parts of the nn- 

 exclted leaf may be partly ex- 

 plained by the migration of 

 water. "For on the one hand 

 we know that In conse<iuence of 

 the surface evaporation, migra- 

 tion of water certainly exists, 

 while on the other we have proof 

 In the experiments of Dr. Kunkel 

 that such migration cannot occur 

 without protludng electrical dif- 

 ferences. In a similar way he Is 

 Inclined to believe that the grad- 

 ual electrical change resulting 

 from repeated excitation, as well 

 as the after effect of a alngU^ ex- 

 citation, are to be explained by 

 migration of water accompanying 

 the motion of the leaf. On the 

 other hand he believes that the 

 primary, and rapidly propagated 

 electrical disturbance which Is 

 the Immediate effect of excita- 

 tion cannot be due to water-mi- 

 gration, but that It Is the ex- 

 pression of molecular changes In 

 the protoplasm of the leaf. Pro- 

 fessor Sanderson takes occasion 

 to correct the Impression pro- 

 duced by certain expressions In 

 his lecture at the Royal Institu- 

 tion in 1874. Professor Munk, 

 among others, seems to have be- 

 lievea that Pmfessor Sanderson 

 claimed absolute Identity l>e- 

 tween muscular action and the 

 movement of the leaf of Dloniva. 

 It nee<l hardiv be stated that no 

 such implication was intended by 

 Professor Sanderson: the view 

 which he hold In 1874 he still ad- 

 heres to. namely, that the rapid- 

 ly propagated molecular change 

 In an excited Dloni^a loaf can 

 only be identified with the corre- 



