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bark wound, this network has an elliptical circumference, the wound being in the 

 lower focus of the ellipse. 



If the stimulus is removed by the cure of the wound, the cambium again con- 

 tinues to produce normal secondary wood, so that afterwards the gum canals may 

 be found in the wood itself. 



If the stimulus continues the gum formation also becomes lasting. 



The stimulus issues from the cells that die slowly by wounding, poisoning or 

 parasitism. Probably a cytolysine flows these cells into the young wood or the pro- 

 cambium; these bind the lysine and liquefy to gum. Hence, gummosis is caused by 

 necrobiose. 



Young medullary rays and phloembundles are with more difficulty converted 

 into gum than the young secondary wood. But in the fruit-flesh of the almond and 

 the peachalmond it is the phloem which changes into gum. The protophloem of the 

 bundles often remains unchanged. 



Although gummosis in these fruits belongs to their normal development, a 

 wound stimulus is nevertheless active. This stimulus springs from the strong tension 

 in the parenchyma of the fruit-wall, which gives rise to tearing, necrobiose and 

 gum formation in the delicate tissue of the phloem bundles. Consequently the 

 wound stimulus is here a normal factor of development. 



It might also be said that the almond and the peachalmond are pathological 

 species, but thereby nothing would be explained. 



M. \V. Beijerinck, Verzamelde Geschriften ; Vijfde Deel. \2 



