No. 83.] 377 
serted under the bark of one to three year old branches of thrifty 
peach trees. In three weeks all but one had apparently become es- 
tablished and new gum added. At the same time some gum from 
the same source was similarly planted under the bark of cherry 
and plum trees; of four plantings, all grew. The microscope 
showed the presence of abundant mycelium and spores, but whether 
of the species found by Beyerinck was not definitely determined. 
In examining flowering almond bushes in June, many branches 
were found to have their terminal portion quite dead, and with an 
exudation of gum at the point between the dead and _the living 
parts. In many cases this was also accompanied by a growth of the 
fruit rot fungus (Oidium fructigenum), it forming minute white 
tufts of spores over the whole surface of the branch from one to six 
inches above the gum. Whether the initiative was due to the punc- 
ture of an insect, occasioning the flow of gum, and this offering a 
favorable medium for the introduction of the rot fungus, all having 
a share in the final killing of the branch, or whether the several 
agents appeared in a different order, it is not our present purpose to 
inguire. The association of the rot fungus with the gumming was 
suggestive, and experiments were instituted to see if any actual re- 
lationship existed. Spores of the fungus were inserted in a slight 
incision of the stem of a vigorous young shoot of cherry, of peach 
and of flowering almond, kept fresh under a bell jar. Other shoots 
of the same sort were infected in the same way with spores of the 
same fungus taken, however, from rotting cherry fruits. All the 
spores germinated readily, and all but one of the cherry shoots 
showed the beginning of rot in the stem in twenty-four hours. Con- 
siderable of the stem and part of the leaves of the peach and of the 
flowering almond shoots were rotten in nine days. The remaining 
cherry shoot rotted about a third of an inch each way from the 
wound in the same time, and besides, what is the interesting point 
in this connection, two small drops of gum had exuded from the 
wound, which had all the characteristics of the usual cherry gum. 
Two days later the larger drop was removed and ‘examined under 
the microscope and found to be permeated with the mycelium of the 
rot. As an isolated case, it is very difficult to say whether the fun- 
gus had any direct influence or not in producing the gum. 
Another set of experiments, primarily undertaken for a different 
purpose, have a direct bearing here. On July 16, a number of in- 
oculations were made on the vigorous growing branches of a peach 
tree, using the viscid exudation from the pear blight, but all of these 
except one (exper. 22) were destroyed by accident. This one did 
not reproduce a blight, but, most unexpectedly, in ten days gave a 
drop of clear amber gum that differed in no perceptible way from 
that produced by ordinary gummosis. The next trials were on July 
24, when five inoculations were made, using an infusion of pear 
blight instead of the exudation and with uniformly the same results. 
One of these was carefully examined in section and bacteria were 
found abundant in a layer lining the wound, but not extending out 
{[Assem. Doc. No. 33.] 
