i6g 



Wound stimulus as cause of gummosis. Poisoning, and 

 parasitism also causes of this stimulus. 



Gummosis in the Amygdalaceae is a process of cytolysis, whereby young cells, 

 freshly sprung from cambium or procambium, and sometimes also young parenchyma, 

 are more or less completely dissolved and converted into canals or intercellular spaces, 

 filled with gum. In dissolved parenchymatous tissues usually remains of not wholly 

 disappeared cell walls are found; the gum of the phloem bundles is more homo- 

 geneous, but always the microsomes of the dissolved protoplasm are found. The 

 nitrogen of the gum springs from the dissolved protoplasm. 



Formerly we proved *) that by such different causes as poisoning, parasitism 

 and mechanical wounding gummosis may be experimentally provoked in many 

 Amygdalaceae, as almond, peachalmond, apricot, peach, plum, cherry, and bird's 

 cherry. 



But these three groups of causes may all be considered from one single point 

 of view, by accepting that gummosis is always the effect of a wound stimulus, pro- 

 ceeding from the slowly dying cells, which are found as well in every wound, as at 

 poisoning and parasitism. These dying cells may change into gum themselves, but 

 besides, exert their influence on cambium tissues to distances of some centimeters. 

 This distance-influence is the principal effect of the wound stimulus. But poisoning 

 by sublimate or oxalic acid, introduced under the bark, can as well excite gummosis 

 as an incision or a wound by burning or pricking. Neither the dead cells nor the 

 poison are the ative factors here; the stimulus proceeds from the slorvly extinguishing 

 cells, so that gummosis is essentially a necrobiotic process. Probably the dying cells, 

 after the death of the protoplasm, give off an enzyme or enzyme-like substance, a 

 lysine, fixed during active life, but, which being freed by necrobiosis and absorbed 

 by the young division products of the cambium causes their cytolysis. This reminds 

 of the cytolysines of the animal body, originating when foreign cells are introduced, 

 which liquefy the corresponding cells, for example the haemolysines which dissolve 

 the red blood-cells. Furthermore of the bacteriolysines and of cytase, the enzyme of 

 cellulose. 



If the hypothesis of the existence of a gumilysine is right, - - and I think it 

 is, - - this substance must be of a very labile nature, for when bark wounds are in- 

 fected with gum, quite free from germs of parasites, no more abundant gummosis is 

 observed than at mechanical wounding only. But a difference, however slight, will 

 certainly exist. 



Gummosis produced by ivound stimulus. 



The influence of this cause is best studied in the following experiment. 

 A deep wound, penetrating into the cambium of a branch of almond or peach, 

 commonly soon heals completely, but it may be that gum flows from the wound. This 



') M. W. Beijerinck et A. Rant. Excitation par traumatisme et parasitisme, et 

 ecoulement gommeux chez les Amygdalees. Archives Neerlandaises, Ser. 2, T. II, 

 pag. 184, 1905. Centralblatt f. Bakteriologie, 2te Abt., Bd. 15, pag. 366, 1905. - 

 A. Rant: De Gummosis der Amygdalaceae. Dissertatie Amsterdam, Bussy, 1906., 



