vi ELECTROMOTIVE ACTION IN VEGETABLE CELLS 31 



be expected, e.g. in the numerous examples of permanent differ- 

 ences in turgor (growing fruits, motor organs of bean, etc.). 



The glandular parts of plants should also be suitable objects. 

 Biedermann found in various species of Drosera that on leading 

 off from the stalk on one side, and the surface of the leaf, which 

 is thickly set with little glands, on the other, there were con- 

 siderable differences of potential. 



The intrinsic nature of the physiological changes of state 

 which underlie the galvanic effects of excitation in the excitable 

 leaf of Dioncea, or pulvinus of Mimosa, cannot with our present 

 knowledge be pronounced upon, any more than in the correspond- 

 ing electromotive activities of animal mucous cells. The wide- 

 reaching analogies in the two cases can hardly be overlooked, 

 as emphasised by Prof. Burdon-Sanderson, who has been good 

 enough to make especial communications on this subject. As 

 in the tongue of the frog, so in the leaf of Dioncea, we find a 

 " current of rest," of which the sign may alter with circumstances, 

 its internal relations with the galvanic excitatory effects being 

 invariable and unmistakable. In both cases, moreover, the effect 

 of excitation is a frequently diphasic variation, the sign of which 

 depends throughout on the state of the organ at the moment. 

 Burdon-Sanderson therefore holds it to be not improbable that 

 in the leaf of Dioncea, as in animal mucosae, the current led off 

 may be the result of two antagonistic chemical processes which 

 occur in the plasma of the cells, and are always simultaneously 

 present. These imply the development of an opposite potential, 

 while to one of them is due the permeability of the cell-wall 

 to water. 



BIBLIOGRAPHY 



1. H. BUFF. Annalen d. Chemie u. Pharmacie. LXXXIX. 1854. p. 76 ff. 



2. TH. JURGENSEN. Stud. d. pbysiolog. Inst. zu Breslau. Part I. 1861. 



3 f L. HERMANN. Pfl. Arch. "iV. p. 155. XXVII. 1882, p. 288, Note. 

 I J. MULLER-HETTLINGEN. Pfl. Arch. XXXI. 1881. p. 193. 



4. A. J. KITNKEL. Pfl. Arch. XXV. p. 342. Arb. d. bot. Inst. zu Wiirzburg, 



II. p. 1. 



5. OTTO HAAKE. Flora. 1892. p. 454 ff. 



6. BURDON-SANDERSON. 



(a) Report of XLIII. Meeting of Brit. Assoc. Bradford 1873. London 1874. 



Tr. of the Section, p. 133. 



(6) Proceedings of Roy. Soc. XXI. No. 147. 1873. p. 495. 

 (c) Centralbl. f. med. Wiss. 1873. No. 53. p. 833. 



