54 
Journal of Agricultural Research 
Vol. XXVI, No. a 
tissue from the lips of the gumming wounds continued until the first week 
in June, after which no change took place. Of a total of 12 inoculations 
9 resulted in eruptions or small galls, 3 formed small gumming cankers 
which remained stationary throughout, while the controls healed over 
normally. Unfortunately, the tree bearing the inoculations was pulled 
up in connection with the building of a new hall for the College of Agri¬ 
culture. Plate 11 shows the condition of the 9 positive inoculations 
on August 10, when they were photographed. 
An examination of the callous which had formed on the control cuts 
showed it to consist largely of wood tissue which had developed to heal 
the cut. In the lesions produced by the inoculations, however, no 
such wood tissue was formed. The interior was filled with gum and the 
swelling was found to be due to growth in the bark. The inoculations 
with Monochaetia sp. into old apricot tissue have thus resulted in abnor¬ 
mal growth identical in all its essential features with that of the galls 
on old Moorpark apricot trees. 
It is interesting to note in this connection that the same organism 
which produced gumming cankers, when inoculated into young plants 
without any formation of abnormal growth, formed when inoculated 
into the branches of an old tree gumming lesions at first, which were 
later followed by abnormal growth. This would seem to indicate that 
the first stage of the disease consists in the breaking down of the affected 
tissue, resulting in a gummosis, and that this period is followed by one 
in which the plant attempts to outgrow the lesion. The formation of 
galls results. Another fact shown by the inoculation experiment is that 
galls may be artificially produced on varieties other than the Moorpark, 
to which the disease is practically restricted in nature. 
On May 19, 1916, when it became apparent that the inoculations on 
the old apricot tree promised to produce galls, a larger number of inocu¬ 
lations, amounting to a total of 100, were made on old apricot trees 
of the Moorpark and Blenheim varieties, at Hayward, Calif. Several 
of these inoculations were believed at the time to have been successful, 
for they were gumming somewhat more abundantly than were most of 
the controls. None, however, produced galls. By the end of the summer 
all of the inoculations showed signs of healing over. The negative 
result of this experiment is attributed to the dry and consequently un¬ 
favorable weather conditions existing at the time the inoculations were 
made, and afterward. As has already been pointed out, infection in 
nature takes place during the winter and early spring, and the spread 
of the disease is proportional, generally speaking, to the humidity of the 
season. 
REISOLATION OF MONOCHAETIA SP. 
In the writer's absence the work of reisolating the causal agent from 
the eruptions resulting from the inoculations with Monochaetia sp. was 
performed by Miss Helen Czarnecki. 
An inoculated branch was soaked for three minutes in alcoholic 
corrosive sublimate (112000 HgCl 2 , in 50 per cent alcohol). The rough 
surface was cut off with a flamed knife and bits of tissue were removed 
from the interior of the bark and planted in standard nutrient broth. 
By this method pure cultures of Monochaetia sp. were obtained in five 
cases out of seven. 
Another inoculated branch was soaked in 95 per cent alcohol for five 
minutes, then passed through the flame and placed in a moist chamber. 
