ADAPTATION 195 



added by the fact that it is a so-called ferment, the diastase, 

 which promotes the transformation of starch into cane-sugar, 

 and that this ferment is actively produced by the organism : 

 but even its production would not prove that any real kind 

 of secondary regulation exists here, if nothing more were 

 known about such an active production than this single 

 case. 



In a special series of experiments almost all carried out 

 in Wilhelm Pfeffer's botanical laboratory at Leipzig, an 

 attempt has been made to discover in what manner the cells 

 of plants are able to withstand very high abnormalities of 

 the osmotic pressure of the medium that is to say, very 

 great changes in the amount of its salinity. That many, 

 particularly the lower plants, are able to stand such changes 

 had been ascertained already by the careful examinations of 

 Eschenhagen ; but recent years have given us a more pro- 

 found insight into what happens. Von Mayenburg l has 

 found that sundry of the species of Aspergillus, the common 

 mould, are able to live in very highly concentrated solutions 

 of several salts (KN0 3 and N"a. 7 SO 4 ). They were found to 

 regulate their osmotic pressure not by taking in the salts 

 themselves, but by raising the osmotic pressure of their own 

 cell sap, producing a certain amount of osmotically active 

 substances, probably carbohydrates. If in this case it were 

 possible to assume that the osmotic pressure of the medium 

 were the real stimulus for the production of the osmotic 

 substances in the cell, stimulus and production both 

 corresponding in their degree, we should be entitled to 

 speak of a primary though physiological 2 regulation only ; 



1 Jahrb. wiss. Bot. 36, 1901. 



2 Carbohydrates cannot be ionised, and therefore there is no doubt that in 



