717 



logical formation of resin is perfectly independent of the presence of normal 

 resin canals. The conditions seem to be more complicated in Peru and Tolu 

 Balsam. 



Therefore, so far as we can examine the pathological formation of resin, 

 it corresponds perfectly to gummosis and, therefore, the same theories, which 

 we have expressed earlier, hold good for it. It is not the wound stimulus 

 in itself which causes the liquefaction of the solid tissues, but enzymatic 

 actions, which we cannot determine at present, manifested in the result that 

 scattered tissue groups fail to develop normally and dissolve because of 

 oxydation. These processes can be introduced by wounds but also arise 

 from a changed nutrition. They are dependent upon a definite develop- 

 mental phase, i. e. the time of the sprouting of the trees. Centres of lique- 

 faction, already existing, may be increased by the transmission of their 

 enzymes to normal, permanent tissue. 



Supplementarily, we will cite a number of phenomena, some of which 

 belong directly to degeneration due to gummosis, and others belong here 

 because we conceive them to be the results of enzymatic disturbances of 

 equilibrium. 



Analogous to the exudation of gum is the exudation of transparent 

 gummy masses in Eleagnus canadensis, occurring especially about the edges 

 of wounds. Frank has described it more exactly. I found the formation 

 of gum in palms, cucumbers, cacti, and hyacinth bulbsV 



I assume an enzymatic disturbance in the heart rot and the black ring 

 condition of the horse radish'^, the glossiness of cacti, orchids, carnations, 

 etc. Conditions of weakness are thus created which render the plant sus- 

 ceptible to parasitic attacks. Wood has referred to this point with especial 

 distinctness : "I called special attention to the fact that plants rich in 

 oxidizing enzymes were morQ sensitive to unfavorable conditions of tem- 

 perature, moisture and especially to insect enemies than plants poor in these 



According: to Comes, the "Brusca of the Oliw" is a decided gummosis. 

 s. Zeitschr. f. Pflkr. 1S99, p. 132. 

 Loc. cit., p. 22. 



