60 Nebraska Agricultural Exp. Station, Research Bui. 12 
had not been sufficiently nourished. Where the cut was made 
straight across the top or bottom of the wound instead of being 
made pointed or where insufficient foliage was left on a branch 
to insure the proper amount of elaborated food materials to 
heal the wounds, cankers appeared almost invariably. 
The unsatisfactory results led to the institution of the more 
fundamental experiments which have already been described, 
together with more minute observations of the treatments 
already made. New treatments were made each season as 
cankers appeared. The same methods were followed except 
that an effort was made to eliminate all discolored wood. In 
all cases the amount of wood free from discoloration was 
measured and the number of annual rings of growth repre- 
sented was noted. In all 115 trees were treated. The total 
number of original treatments was 341. Of these 22 were re- 
treated three times, 105 were re-treated twice, and 214 were 
re-treated once. This totaled 831 treatments. 
In so far as the beneficial effects of the various covers and 
disinfectants used are concerned table 15 may be taken as 
representative of the treatments made after 1912. Whether 
or not canker hyphae were left in the tissues at the time of 
treatment was found by close observation and microscopic ex- 
aminations to be the determining factor. The effect of either 
covers or disinfectants was practically negligible where in- 
fected wood was left. 
A number of artificial infections in young trees in the 
greenhouse were treated but not covered. In some the dis- 
colored strands were all removed while in others a small 
amount of the discolored wood was left. In all cases fungous 
growth continued from the remaining discolored wood while 
no evidence of the disease could be found in the trees where 
the discolored wood had all been removed. 
It was found that the fungous growth was more rapid near 
the treatments than in similarly cankered limbs where no 
wounds were made. This was no doubt due to the fungus 
being able to secure oxygen more readily. A number of 
wounds were made in pairs in branches which contained myce- 
lium close to the surface. One of each pair was disinfected 
and covered in the same way that canker wounds were treated 
while the other was tightly wrapped and waxed over to exclude 
air. In practically every case characteristic cankers formed 
about the wound which was not tightly wrapped. A few of 
the wrapped wounds also developed cankers, but such cankered 
