116 Butlr.—A Study on Gummosis of Prunus and Citrus, with 
in which the cut surfaces were protected from the air (oxygen), whereas in 
the witnesses from 14% to 100% of the cuttings showed the characteristic 
lesions. Taking the most extensive experiment recorded the witnesses 
showed approximately a mean of 67 % diseased cuttings. 
Sorauer! in his Handbuch der Pflanzenkrankheiten, art. ‘Gummi- 
fluss. der Kirschen’, described the usual appearance of diseased tissues, and 
ascribed gum formation to a latent capacity possessed by embryonic and 
full-grown cells to produce gum. He did not lay any stress at all upon the 
development of gum pockets in the wood in formation, as may be gathered 
from the summary of his observations, which may be translated thus: 
(1) gum formation is preceded by a development of parenchymatous 
tissue within the xylem which presents a nidulose appearance, and lies 
usually between two medullary rays, and exceptionally includes one or 
more ; (2) the abnormal parenchyma develops independently of wound 
stimuli ; (3) the tissues finally break down into gum and the medullary 
rays grow out into the pockets thus formed. 
Sorauer believed that gum formation was due pro parte to a zymo- 
genetic substance present in embryonic and fully developed cells, which 
became active when certain life functions connected with the growth of the 
cell-wall were interfered with. But the retardation in the development of 
the cell-wail thus brought about, as also the transformation of the part 
already laid down into gum, could also be readily accounted for, he thought, 
by assuming an increase in the oxygen supply irrespective of the action of 
enzymes, an opinion also held by Ruhland, as we have seen. This necessary 
supply of oxygen was obtained directly from the atmosphere through the 
intermediation of wounds, or from organic or inorganic stimuli. 
In order to show that gummosis followed stimulation by an oxydizing 
agent, Sorauer performed the following experiment: He made two incisions 
into the limb of a healthy cherry-tree: into one he poured oxalic acid and 
into the other, which was to serve as witness, distilled water. The wound 
treated with oxalic acid gummed freely during the course of the summer, 
the flow only ceasing when the acid had become, in the course of time, 
neutralized ; whereas the witness remained healthy. 
II. GUMMOSIS. 
Syn.: France: Colle, Gommose, Maladie de la gomme; Germany: 
Gummifluss, Gummikrankheit, Gummosis; Great Britain: Gumming, 
gummosis, gum disease, sore shin, foot-rot (erroneously) ; Ltaly: Mal di 
gomma, Male della gomma; Portugal: Lagrima; Spain: Enfermedad. 
1 Sorauer, P. : Handbuch der Pflanzenkrankheiten, i, 1909, pp. 693-7or. 
