172 



described the relation of mechanical wounding to gummosis. But he did not think of 

 poisoning experiments, nor has he any belief in the influence of parasitism on gum 

 formation. W i e s n e r , in his recently published paper on gums in the new edition 

 of his Rohstoffe des Pflanzenreichs, is also of the same opinion as M i k o s c h. 



For my object a short discussion of a few examples of parasitism will suffice. 



The little caterpillar Grapholitha weberiana makes borings into the bark of 

 plum and apricot, and if the outermost corklayer is removed by shaving it off, the 

 butterfly finds so many fit places for deposing its eggs, that the larvae creep in by 

 hundreds and make new borings from which later the gum flows out. These holes 

 are coated with a layer of slowly dying cells, whence the stimulus extends, which 

 produces the gum canals in the contiguous cambium. By cambium I simply under- 

 stand the not yet differentiated division products, young wood and young phloen- 

 terma. The necrobiotic cells, clothing the continually extending holes in the bark, 

 and the great numbers of new individuals of the caterpillars, make the gum pro- 

 duction a chronical process. 



To explain the formation of the enormous quantities of gum produced in this 

 way, it seems only necessary to tink of mechanical wounding and not of any special 

 excretion from the animal. But it must be noted that the space, where the cater- 

 pillar lives during its growth, namely a vertical narrow canal in the innerbark, very 

 near to the cambium, could not possibly be imitated artificially. 



Much more common and interesting than the animal parasites are the gum pro- 

 ducing Fungi of the Amygdalaceae, five of which are found in our country 1 ). The 

 commonest and most vigorous is Coryneum beijerinckii O u d e m a n s (Clastero- 

 sporium carpophilnm A d e r h.) -). 



Pure cultures of Coryneum in bark wounds of almond, peachalmond, peach, 

 cherry plum, bird's cherry, sloe, virginian plum, develop with remarkable quickness 

 and soon make the bark die off, evidently in consequence of the secretion of a 

 poison. Around the dead cells the necrobiotic are found from which the stimulus 

 issues, which, penetrating into the cambium in the usual way, forms gum canals in 

 the young wood. Many mycelial threads of the parasite itself are then cytolised and 

 converted into gum. I think this fact remarkable and a strong argument for the 

 material nature of the stimulus. 



') Coryneum beijerinckii Ou dem ans , Cytospora leucostoma Per soon, Monilia cinerea 

 Bonorden, Monilia fructigena Bonorden and Botrytis cinerea Per soon (see Rant, 

 1. c. p. 88). German authors also mention bacteria as instigators of gummosis, I never 

 found them. 



-) Beij erinck, Onderzoekingen over de besmettelijkheid der gomziekte bij planten. 

 Versl. d. Akad. v. Wetensch. Amsterdam, 1883. Contagiosite de la maladie de gomme 

 chezles pi antes. Archives Neerlandaises, i"eSer.,T. 19, pag. i, 1880. C. A.J. A. Oudem ans, 

 Hedwigia, 1883, N. 8. Saccardo, Sylloge Fungorum, Vol. 3, pag. 774, 1884. 

 Aderhold, Ueber Clasterosporium carpophilum (Lev.) Aderh. und dessen Beziehung 

 zum Gummifluss des Steinobstes. Arbeiten der Biolog. Abt. am Gesundheitsamte zu 

 Berlin. Bd. 2, pag. 515, 1902. Aderhold has experimented with pure cultures of Coryneum, 

 which I had made and sent him. He himself has not executed any isolations of gum 

 parasites. His determination as Clasterosporium amygdalearum (Lev.) is thus founded 

 on the imperfect descriptions from the older mycological literature, in which Oudemans 

 was no doubt better at home than he. Like Lindau I reckon Clasterosporium to another 

 family than Coryneum. 



