81 



From the title of the f irst-mentioned article i) , it appears already 

 that Beijerinck's views had broadened during the twenty years in 

 which he had let the problem rest ; no doubt the pubhcation of Frank 2) , 

 and also the treatise of Aderhold {l.c), had been of influence. 



Beijerinck and Rant described carefuUy how gum-formation 

 occurs through in jury of the cambium of the Amygdalaceae, and de- 

 scribed the changes in the tissue which become visible thereby. They 

 argued, among other things, that the "wound stimulus" makes itself 

 apparent by a gum-formation, covering an area which is limited by a 

 vertically stretched "ellipse", the wound being at the lower focus of 

 this ellipse. Burning, and especially the application of poison (corros- 

 ive sublimate) to a wound, increased gummosis greatly. No influence 

 wasasstrong, however, as an infection with C. Beijerinckii, from which 

 Beijerinck and Rant concluded that this organism produces a 

 violent poison, with a traumatic effect of long duration. The similarity 

 of the results of various causes on this gum-formation then led Beije- 

 rinck and Rant to the conclusion that — in contradistinction to 

 what Beijerinck had thought originally — the cause must not be 

 sought in the specific action of the poison produced by the fungus, 

 but that in all cases the change in the cells which leads to gum- 

 formation should be the result of the production of toxic substances 

 by the dying cells. Gummosis, therefore, should be a process of 

 "necrobiosis", that is (according to Beijerinck's definition), a cell- 

 function which continues after the death of the protoplasm. 



The toxic products produced by this protoplasmic death should 

 react with especial intensity with tissue that is still dividing. The 

 walls of the secondary wood which is being formed by the cambium 

 should be especially susceptible of changing into gum. This reaction 

 with the walls should be in itself — according to Beijerinck and 

 Rant — nothing other than a normally-progressing process in the 

 tissues, where sometimes only a small quantity of cell-wall material 

 changes into gum and is absorbed, and where in other cases only so 

 much gum is produced that the cells or the vessels are filled there- 

 with. Gummosis should therefore mean an excessive activity in the 

 formation of this "cytoclastic" product. 



Finally we mention that Beijerinck and Rant emphasized the 

 similarity between gum-flow and resin-flow, and that here again they 

 called attention to the practical significance of this process. 



Once more — -in 1914 — Beijerinck returned to the subject of 

 gummosis ^), and this time also the publication proved to be an en- 



1) M. W. Beijerinck und A. Rant, Wundreiz, Parasitismus und Gummifluss 

 bei den Amygdaleen, Centralblatt für Bakteriologie und Parasitenkunde, II. Abt., 

 15, 366-375, 1906. In Verzamelde Geschriften 4, 267-277 the French translation 

 which appeared in Archives Néerlandaises des Sciences Exactes et Naturelles, Sér. 

 2, 11, 184-194, 1906 is inserted. 



2) A. B. Frank, Die Krankheiten der Pflanzen, 2. Aufl. 1895. 



3) Gummosis in the fruit of the Almond and the Peachalmond as a process of nor- 

 mal life, Proceedings of the Section of Sciences, Kon. Akademie van Wetenschappen 

 AmsteiHam 17, 810-821, 1914 {Verzamelde Geschriften 5, 168-177). 



M. W. Beijerinck, His life and his work. 6 



