GUMMOSIS 61 



purpose to direct attention to certain questions raised in the mind 

 of the writer during the reading of this memoir. . 



The salient features regarding the conditions which induce gum- 

 mosis, as well as regarding the origin and composition of the 

 gum, according to Butler's account, are as follows. It has been 

 clearly shown that two conditions are essential to the develop- 

 ment of gummosis. These two conditions are filled if, at once, 

 the cambium is active and the tissues are in a high state of sapid- 

 ity. Gummosis is due to the dissolution by hydrolysis of the walls 

 of the embryonic wood. There occurs first a swelling, followed by 

 a gelatinization of the primary membrane. Both membranes are 

 rendered semi-fluid by a further absorption of water. The result- 

 ing solution collects between the contiguous cells and as a result 

 they are detached from each other. The dissolution of the "third" 

 lamella 2 proceeds centripetally. The gummy mass is therefore a 

 mixture of the hydrolyzed cell-walls and the protoplasm of the 

 disorganized cells. 



Ruhland was of the opinion, from experimental evidence, that 

 atmospheric oxygen, when it is permitted to penetrate to the 

 young wood, acts upon the carbohydrate of the cell membrane 

 and of the cell contents and oxidizes them into gum. Chemical 

 analyses show, however, that these gums are hemi-cellulose 

 derivatives and not oxidation products of carbohydrates. Sor- 

 auer was able to show that gummosis followed stimulation by an 

 oxidizing agent. He believed, however, that this agent merely 

 interfered with certain functions of the cell in such a way as to 

 render active some zymogen already present in the cell. All the 

 evidence points to the conclusion that while gummosis is in a 

 certain sense autogenetic, yet it only results because of unusual 

 stimuli. The relation between cause and effect in natural phe- 

 nomena is often difficult to perceive or not easily explicable. For 

 example the formation of zoospores in plants like Ulothrix and 

 Hydrodictyon may be induced by weak solutions of sugar. 



The Arabs have for a long time by empirical methods rendered 

 dates non-astringent by treatment with the. fumes of vinegar. 



2 This terminology is unusual and the figures which accompany the paper do 

 not indicate the corresponding structures. 



