1008 



Botany. — "On tlie TicguJation of the trampiration of Viscum 

 album and Rliipsalls CassytJia'. A contribution to the knowledge 

 of die antagonism between die guard cells of the stomata 

 and the adjacent cells of the epidermis. By Z. Kamerling. 

 (Communicated by Prof. Bkijerinck). 



(Communicated in the meeting of Jan. 31, 1914). 



In recent years I have conducted numerous experiments to obtain 

 an insight into the need for water and the consumption of water in 

 various tropical plants. In continuation of these investigations, carried 

 out in Java and in Brazil, similar experiments have been undertaken 

 during the last few months in Holland with native plants. The 

 method of inquiry was almost always the same : leafy boughs were 

 cut off and hung up in the laboratory in the shade or exposed to the 

 sun in the habitat of the plant investigated ; they were weighed 

 periodically at shorter or longer intervals. 



By this method of exj)erinient the extent of transpiration can be 

 determined when the tissues of the plant still possess their normal 

 water-content and also the nature of its moditication, when the tissues 

 of the plant gradually lose water. 



These experiments shew that in many plants there is a continuons 

 and very considerable transpiration from the beginning of the expe- 

 riment until the leaves of the bough are dried up. In other species 

 the transpiration is moie or less great at the beginning, but decreases 

 gradually so that finally it sinl<s to a minimum-value. This decrease 

 or regulation of transpiration is evidently due to the narrowing or 

 closing of the stomata, which in the different plants investigated may 

 occur more or less quickl}^ and more or less extensively. 



In some plants I found that in contrast to the normal course 

 of the regulation, the intensity of transpiration increases distinctly at 

 the beginning and only afterwards diminishes in the usual way. 

 Such an irregularity, at least when there is no external influence at 

 work, such as temperature, illumination or conditions of humidity 

 or movement of the atmosphere, can hardly be explained otherwise 

 than by assuming that the aperture of the stornata in these cases first 

 dilates when the plant begins to wither and only afterwards constricts. 



I observed this phenomenon very clearly in Viscum album in a 

 comparative experiment which T performed on the transpiration of 

 this plant and of some deciduous and evergreen woody plants. 



It is unnecessary to publish here the detailed results. I append 



