750 NOTES 



338. Townsend : P.J. 30, 1807. Cf. also Pfeffer : Sitzb. sachs. Ges. 1896. 



339. Nemec : Die Reizleitung u. d. reizleitenden Strukturen b. d. Pflanzen, Jena, 

 1901. Id. Biol. Centr. 21, 1902. Cf. also Haberlandt : Biol. Centr. 21. Id. Ber. 

 19, 1901. Id. I.e. [274], pp. 149 sqq. 



340. Batalin : I.e. [298]. 



341. G. Haberlandt : Ann. Buit. 1898 (Suppl. II.). 



342. Rothert : Conn's Beitr. 7, 1896. 



343. F. W. Oliver : Ber. 1887. 



344. G. Haberlandt : Das reizleitende System d. Sinnespflanze, Leipzig, 1890 

 (and the literature there cited). MacDougal : B.G. 22, 1895. MacDougal adduces 

 the following experimental evidence against the author's theory of stimulus- trans- 

 mission in Mimosa. 



1. If water is suddenly forced into the cut end of a stem, by means of a pump, 

 under a pressure of 3 to 8 atm (?), no response follows. Fitting (see below) has 

 pointed out, that the result of this experiment does not really militate against the 

 author's theory, because the water forced in does not move in the secretory sacs, 

 but in the wood- vessels. Fitting himself was unable to force water through the 

 rows of secretory sacs under a pressure of 2 atm. As a matter of fact, when a stem 

 of Mimosa is cut through, the ends of the intact secretory sacs next the cut surface 

 quickly become occluded by plugs of resinous material. This point was explained 

 by the author in his above-mentioned treatise (p. 19). 



2. If the base of a cut stem is scraped, so as to expose the secretory sacs, and then 

 immersed in a saturated solution of potassium nitrate, after allowing the leaves 

 to unfold no response follows. In devising this experiment, MacDougal evidently 

 started from the erroneous assumption that plasmolysis could produce a rapid 

 fall of hydrostatic pressure in the system of secretory sacs. For stimulation only 

 follows upon the sudden deformation of the sensitive cells in the pulvini produced 

 by a wave of pressure ; the fall of pressure produced by plasmolysis is much too 

 slow to act as a stimulus. Fitting repeated MacDougal's experiment in a modified 

 form, and occasionally obtained positive results {i.e. a response) ; but microscopic 

 examination showed that, in all such cases, the secretory sacs had died after being 

 plasmolysed. These instances are therefore really special cases of stimulation by 

 poisonous or corrosive substances. This point had also been discussed by the author 

 in his above-cited treatise (pp. 61 sqq.). 



Fitting : P. J. 39, 1903. While Fitting arrives at no definite conclusion regarding 

 the mode of stimulus-transmission in Mimosa pudica in this paper, his conclusions 

 agree in many points with those of the author. In particular, he thinks it probable 

 that the transmission depends upon the " movement of a liquid in living cells." 

 though he does not clearly specify the cells that are concerned in the process ; in this 

 connection it should be borne in mind, that the drop of liquid which suddenly exudes 

 when a stem or leaf is cut, is certainly almost entirely derived from the secretory 



sacs. 



It should be noted that, according to the author's observations (I.e. pp. 63 sqq.), 

 the woody cylinder of Mimosa pudioa is capable of transmitting stimuli to some 

 extent; for a traumatic stimulus is still transmitted by a stem in which the 

 continuity of the secretory tissue has been interrupted. The author has endeavoured 

 to give an explanation of Ibis rather remarkable phenomenon in bis above- 

 mentioned treatise. 



