72 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



by the previous workers on the subject. The marked 

 acceleration in the clumping caused by calcium, strontium, 

 or barium, need not mean that their ions are in any way 

 connected with the action of pectase, but is apparently 

 fully explained by the well-known property of divalent 

 ions in causing the clumping of colloids with a far greater 

 rapidity than do monovalent ions. The presence of cal- 

 cium salts in quantity evidently causes flakes of coagulum 

 to appear even when the action of the enzyme has been in 

 progress for a short time only. 



DISCUSSION OF THE FORM OF THE VISCOSITY CURVES. 



Ball has suggested that the product of the action of 

 pectase on pectin consists at first of separate colloidal 

 particles, and has pointed out that during their formation 

 there is practically no change in viscosity, as shown by the 

 initial portions of the curves being almost parallel to the 

 time axis. This is succeeded by a portion of the curve 

 which shows rapid increase in viscosity, the physical in- 

 terpretation of which he considers may be the union of 

 adjacent particles to form a loose network, the individual 

 meshes of which are continually becoming smaller by sub- 

 division through the attachment of freshly formed material. 

 Since Bertrand and Mallevre have shown that gelatiniza- 

 tion does not occur when all traces of electrolytes have 

 been removed, it is possible that the building of the network 

 is due to their activity. As an alternative explanation, the 

 view has been advanced that the enzyme itself looses its 

 activity when electrolytes are entirely removed, for it is 

 well known that other enzymes become enfeebled when 

 their ash content is reduced below a certain point. The 

 constituents of the ash may of course be in combination, 

 and not dissociated, though in most cases it is probable 

 that they are partly in the state of dissociable metallic 



