376 [ ASSEMBLY 
Most recent, as well as earlier writers, consider the exudation of 
gum in stone- fruited trees as pathologie, arising from some abnormal | 
process or influence in the plant. The exact method by which the 
gum is produced is now through the investigations of Wigand, 
Frank and Prillieux very well known. It is found to proceed from 
a deorganization of the walls and contents of the cells, beginning in 
the wood and involving the bast and bark, and in severe cases the 
cambium also, the star ch and other contents of the cells being at the 
same time included in. the general change. The physiological sig 
nificance of this process has recently been studied at the agricul- 
tural Hochschule at Berlin, under Frank’s direction,* and the con- 
clusion reached is that the production of gum where a wound has 
occurred is quite universal in woody plants, and serves as a protec- 
tion to the exposed surface during the process of healing. It is, 
therefore, the excessive production of it that is harmful. This 
narrows down the inquiry very materially, for we have now only to 
investigate the cause of this increased activity which has changed a 
normal into an abnormal process, often causing an enormous waste 
of material that would have otherwise gone to the production of 
healthy tissues. Frankt is of the opinion that it isa symptom of the 
weakened vitality of the tree arising from some additional cause, 
and that, therefore, in order to prevent or cure the malady it is nec- 
essary to first restore the tree to health, when the gumflux can be 
easily checked. 
A year ago Dr. Beyerinck of the agricultural school at Wagen- 
ingen, Holland, conceived the idea that the production of gum 
might be caused by bacteria. By experimenting he found that the 
disease could be started in any of the plum family by inserting a 
little of the gum into a fresh incision, but that if the gum be first 
thoroughly: heated no change takes place. This pointed directly to 
some living contagium, and in searching for it he finally fixed upon 
one of the higher fungi, instead of bacteria, whose mycelium and 
spores appear ed to always be present.{ The fungus was described 
as a new species of Coryneum (C. Beyerinckii) by Oudemans.§ 
The occurrence of mycelium in the gum is no new discovery, as 
spores are very easily caught in so viscid a substance, and many find 
it a favorable soil in which to grow. As longagoas 1855 Berkeley| 
ealled attention to the abundance of mycelium, especially in some 
chérry gum from South Carolina; but it was not considered as in 
any way related to the pr oduction of the gum. 
The following experiments were tried at the station: June 1%, 
small pieces of peach gum not exceeding the size of a pea were in- 
* Cf. Botanisches Centralblatt, XX, p. 194. 
+ Krankheiten der Pflanzen, p. 93. 
¢ Cf. Gardeners’ Chronicle, xt p. 238 ; I have not seen the author's original 
paper, Onderzoekingen over ‘de Gomziekte bij Planten. 
S Hedwigia, 1883, p. 1138; Plowright, in Gardeners’ Chronicle, X XI, p. 410. 
Taenlnee Chronicle, 1855, p. 205. 
