66 FREDERICK A. WOLF 



in its formation from the initial stages of gummosis until they 

 finally vanish upon the gelatinization of the tertiary membrane." 

 The fact that he finds no gum in the protoplast cannot be taken 

 to prove that the protoplast takes no part in gum formation. All 

 that such a micro-chemical test proves is that there is no gum with- 

 in the protoplast. This is not at all surprising and is exactly 

 in accordance with the conclusions of other investigators of the 

 secretory products of plants. Tschirch 13 states that the presence 

 of resins is not the direct result of protoplasmic activity but of 

 enzymotic activity within the wall itself. 



In conclusion, therefore, there appears to be no reason, in the 

 evidence submitted, for disbelieving the role of enzymes. Until 

 the immediate cause of gummosis is demonstrated to the exclu- 

 sion of enzymotic activity, it remains more reasonable to adhere 

 to a view which, at any rate, has the support of a large body of 

 collateral evidence to substantiate it. 



13 Tschirch, A., Die Chemie und Biologie der pflanzlichen Sekrete. Leipzig, 

 1908. 



