24 Nebraska Agricultural Exp. Station, Research Bui. 12 
The foregoing data clearly indicate that the fungus is a 
wound parasite and that the older the tissues exposed by- 
wounding the greater is the danger of infection. All wounds 
are liable to infection, and since wood older than five years 
is the most susceptible it is especially dangerous to leave large 
pruning wounds unprotected. 
It is evident that the disease may be disseminated by means 
of ascospores and conidia, and by infected particles of wood 
which may cling to the pruning tools. On account of their 
greater virility ascospores are perhaps the greatest menace, 
altho even with the short period of time during which they are 
viable, conidia offer a great source of infection due to the fact 
that they are formed in such large quantities over a long 
period of the growing season. 
ROOT INOCULATIONS 
Inoculations were made with ascospores in roots of Jona- 
than and Ben Davis trees, with the same general results. It 
was impossible to infect roots near their rapidly growing tips, 
and one-year-old wood was found to be very resistant. Shal- 
low roots were always more susceptible than those 12 or more 
inches below the surface of the soil. However, this was mani- 
fest by the slow progress of mycelium in deep roots as com- 
pared with the rate of growth in roots near the surface more 
than by the number of effective inoculations. The percentage 
of effective inoculations was much lower in all roots than in 
the portion of the tree above ground. In the roots 39.4 per 
cent were effective as compared with 75.27 per cent in the 
trunk and branches. 
DETERMINATION AND IDENTIFICATION OF INFECTION 
In order to determine the number of inoculations which 
produced infection it was necessary to section and stain the 
wood and examine it under the microscope. At first the 
fungus-bearing tissues were killed by the use of formalin and 
alcohol, corrosive sublimate, and picric acid and corrosive 
sublimate. The formalin alcohol solution proved the most sat- 
isfactory since no washing or clearing was necessary before 
sectioning. An attempt was made to conserve time and labor 
still more, since there were so many inoculations to be exam- 
ined, by sectioning the wood without killing. This proved so 
satisfactory that with the exception of a few which were run 
thru the celloidin process all the remaining specimens were 
treated in this way. The sections were cut with a sliding 
microtome using a very heavy blade. 
