BOOKS AND CURRENT LITERATURE 



Response in Dionaea and Drosera. — Two recent papers, one by 

 Brown^ and the other by Hooker^ deal with the physiology of move- 

 ment in leaves of Dioncea and in tentacles of Drosera. 



Brown finds that Dioncea leaves grow at an increased rate during 

 the reaction to a stimulus, the enlargement of the lower surface during 

 closure and that of the upper surface during opening soon becoming 

 permanent. Whether a leaf may close without permanently enlarging 

 is not considered in this paper, although the measurements seem to 

 show that enlargement becomes less during successive reactions. This 

 may suggest either that the permanent enlargement is purely inci- 

 dental or, more probably, that the active tissue is capable of but few 

 responses. The percentage of increase in width of the lower surface 

 was found to be 13.0, 9.0, 3.2, for three apparently successive closures 

 of the same leaf. 



The statement that enlargement occasions the movement in Dioncea 

 affords an exception to the apparently almost general rule that re- 

 sponse to shock stimuli is accomplished by a contraction of the motor 

 tissue as a whole. However, it may be found that the accelerated 

 metabolic activity of carnivorous plants during reaction, as shown by 

 the formation and secretion of proteolytic enzymes and the like, may 

 give rise to an accelerated growth rate. Hooker's observation, that 

 Drosera tentacles retain their curvature when plasmolyzed soon after 

 movement has been completed (see following review), may support 

 this supposition. 



Perhaps the most striking feature of Brown's paper is his treat- 

 ment of the processes preceding the condition of permanent enlarge- 

 ment, so often loosely summed up in papers on similar subjects as 

 "growth changes." He considers three groups of changes, one or 

 more of which may possibly occasion the movement. (1) A sudden 

 increase in the turgor of the motor cells may cause stretching of the 



^ Brown, William H., The mechanism of movement and the duration of the 

 effect of stimulation in the leaves of Dionaea. Am. Jour. Bot. 3:68-90. 1916. 



^Hooker, Henry I)., Jr., Physiological observations on Drosera Rotundifolia. 

 Bull. Torrey Bot. Club 43: 1-27. 1916. 



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