1012 



We see here also how th? intensity of transpiration increases 

 when the plant investigated has lost + i V2 7» of its wei^i-ht and 

 then later decreases (when the loss by tians[)iration has risen to 

 + 6 7o). Simultaneously with this experiment on R/iipsalis Cassytlui 

 some other plants {Pothos aiireK, PJdlodendron spec, Aechmea spec., 

 Vriesea spec, div.) were investigated by the same method, without 

 showing this peculiar irregularity in the transpiration. 



It may dearlj- be assumed that in the case of Viscum album and 

 Wdpsalis Cassytlui we have to deal, with the antagonism between 

 the guard-cells of the stomata and the adjacent epidermal cells, 

 which has been often mentioned in the literature, but nevertheless 

 remains the subject of controversy. The epidermal cells next to the 

 stomata are in both plants differentiated from the other epidermal 

 cells, and are developed as so-called subsidiary cells of the stoma 



As my considerations and conclusions are limited to the plants 

 investigated, it would lead us too far afield to (juote the whole 

 literature of the mechanism of the stomata; it will be enough to 

 characterise the current view of the antagonism between the guard- 

 cells and the adjacent epidermal cells. 



MoHL and Leitgeh have assumed, partly on the evidence of expe- 

 riments with isolated pieces of epidermis, that the stomata are passively 

 closed through the turgor of the adjacent epidermal-cells. 



ScHWENDENF.R and his school on the other hand defended the view 

 that the subsidiary cells are of little oi- no importance for the sto- 

 matal mechanism. 



Pfeffer ^) in 1897 in a survey of these views pointed out that the 

 results of these various investigators only differed quantitatively and 

 that in experiments with isolated pieces of epidermis the different 

 rate of water-absorption in the various cells may have a great in- 

 fluence on the phenomena which 'are observed in the stoma. 



Benecke *) in 1892 published a special study of the subsidiary 

 cells of the stomata, and came to the conclusion that the subsidiary 

 cells have in Succulents the function of eliminating the influence on 

 the stomata of pressure and tensioji, which in consequence of the 

 crumpling of the leaves through loss of water, are set up in the 

 epidermis. 



Benecke scarcely touches on the question of the antagonism between 

 guard-cells and subsidiary cells-. "Wir verfolgen diese StreitfVage 

 "über die Bedeiitung der Nebenzellen hier nicht weiter sondern 



1) Pfeffer, Pflanzenphysiologie. Zweite Auflage 1897, Erster B.ind, S. 173. 



2) Benecke, Die Nebenzellen der Spaltöffnungen, Botanische Zeitung 1892. 



