146 MOVEMENTS OF CURVATURE 



tentacles of Drosera, but probably positive results could be gained by 

 properly graduated and applied induction-shocks. 



According to Mohl J , constant electrical currents are without effect upon 

 tendrils, but it is not certain whether the tone, and hence the power of 

 response to various stimuli, may be modified by a continuous current, 

 or by the continued application of induction-shocks. According to Kabsch 2 , 

 the lateral leaflets of Desmodium gyrans, which have become motionless 

 at 22 C., are caused to move by weak induction-shocks, but further investi- 

 gation of this phenomenon is required. It is not, however, surprising that 

 induction-shocks should act like a blow and excite the rapid movement of 

 the gynostemium of Stylidium, or the sudden dehiscence of the fruit of 

 Impatiens 3 . 



PART VI 



DEHISCENCE AND DISPERSAL MOVEMENTS 

 SECTION 31. Special and General. 



The modes of dehiscence of fruits, anthers, sporangia, the splitting 

 of the integuments of seeds and of the membranes of spores, as well as 

 the mechanisms of dispersal of seeds, spores and other reproductive bodies 

 are all of great biological importance 4 . In most cases, however, the 

 phenomena are physical in origin, but even here the development of the 

 requisite physical conditions is a physiological problem. 



The hygroscopic movements of dry fruits, of the carpellary beaks of 

 Erodium, and of certain hairs are the result of unequal imbibition and 

 swelling, whereas in other cases the fall of turgor consequent upon the 

 death of certain cells may result in purposeful movements or may aid in the 

 rupture of tissues. Even without actual death, movements may result 

 from the liberation of strains set up by attempted growth. It is in this 

 way that the rapid movements of the stamens of Parietaria and the sudden 

 dehiscence of the fruit of Impatiens are brought about. In these cases 

 the active tissues remain living, whereas the sudden escape of the contents 

 of the dehiscing spore-sacs of certain Ascomycetes is connected with the 

 death of the sac. In neither case, however, can the process be repeated, 

 since even where: the active tissues remain living they are no longer 

 capable of reproducing the requisite tissue-strains. This does, however, 

 occur during the autonomic movement of the gynostemium of Stylidium, 

 which is able to perform repeated sudden movements. 



In all such movements not only the strains but also the conditions for 



1 Mohl, Ranken- und Schlingpflanzen, 1827, p. 70. 2 Kabsch, Bot. Ztg., 1861, p.^6i. 



3 Kabsch, 1. c., p. 358. 



* See the accounts given by Ludwig, Biologic d. Pflanzen, 1895, pp. 296, 326 ; Kerner, Pflanzen- 

 leben, 1891, Bd. I, u. 2 (Natural History of Plants, 1895, Vol. II, pp. 91, 140, 429, 833). 



