SPECIAL AND GENERAL ACTIONS 145 



but possibly more intense and prolonged etherization might have this 

 effect. The anaesthetized tentacles of Drosera become in some cases 

 inexcitable, but not always 1 . It is, however, not certain whether ether 

 and chloroform suppress the excitability of tendrils and of the tentacles 

 of Drosera before the power of growth is lost Czapek 2 finds that the 

 power of geotropic curvature is sooner and more readily inhibited by 

 anaesthetics than the power of geotropic sensation. Hence by applying 

 appropriate concentrations of chloroform to the radicles of Vicia Faba and 

 Lupinus albus it is possible to subject them to geotropic induction, which 

 only finds visible expression when the chloroform is removed. Similar 

 results may be obtained by the use of carbon dioxide, caffein, and a few 

 other substances, as well as by low temperatures, not only with the radicles 

 but also with the sporangiophore of Phycomyces*. In the case of the 

 pulvini of Mimosa pudica, however, the loss of the power of response is due 

 to the interference of the anaesthetics with the process of sensation. 



Electricity. From the available but incomplete researches on the 

 general action of electricity on growth it may be concluded that the 

 varying kinds of curvature are not appreciably affected by weak constant 

 currents, and that stronger currents retard curvature and ultimately act 

 injuriously or fatally. It is, however, uncertain whether a particular inten- 

 sity of current may act as an excitation and awaken curvature. 



Electrical discharges and induction-shocks act like mechanical exci- 

 tations. Hence the full amplitude of movement is produced in the 

 pulvinus of Mimosa pudica and in the stamens of Centaurea and Berberis 

 by a single make- or break-shock, whereas repeated induction-shocks are 

 required to produce a similar effect in the pulvini of leaflets of Oxalis 

 acetosella and other species of this genus 4 . Continued induction-shocks 

 act in the same way as repeated blows upon the leaves of Mimosa 

 pudica, which in both cases become inexcitable and, accommodating them- 

 selves to the continued stimulation, re-expand and return to their original 

 position 5 . Sensitive tendrils are stimulated to curvature by weak induction- 

 shocks 6 , although Hofmeister 7 was only able to obtain this result by using 

 strong induction-shocks. Nitschke 8 obtained negative results with the 



1 Darwin, Insectivorous Plants. Cf. also Heckel, Compt. rend., 1876, T. LXXXII, p. 525. 



2 Czapek, Jahrb. f. wiss. Bot., 1898, Bd. xxxn, p. 199. 



3 Steyer, Reizkriimmungen bei Phycomyces, 1901, pp. 7, 25. Cf. also Correns, Flora, 1892, 



P- 134- 



* The older literature is given in the works already quoted of Treviranus, de Candolle, &c. 

 Cf. also Kabsch, Bot. Ztg., 1861, p. 358 ; Cohn, ALhandlg. d. schles. Ges. fur vaterl. Cultur, 1861. 

 Heft i, p. 21 (Stamens of Cynareae) ; Blondeau, Compt. rend., 1867, T. LXV, p. 304; Pfeffer, Unters. 

 a. d. bot. Inst. zu Tubingen, 1885, Bd. i, pp. 505, 521. 



5 Cf. Pfeffer, 1. c., p. 521. 6 See Pfeffer, 1. c., p. 505. 



7 Hofmeister, Pflanzenzelle, 1867, p. 313. s Bot. Ztg., 1860, p. 229. 



PFEFFER. Ill 



