272 
Journal of Agricultural Research 
Vol, IX, No. 8 
Trees may remain in normal health for 15 to 30 years before becoming 
diseased if set soon after the timber has been removed. Trees in 
orchards which are well cared for appear to be as subject to disease as 
those in neglected orchards. Not more than four trees in a group have 
been found to be diseased, and more often such trees stand singly. It 
is indicated that the dissemination of the disease is accomplished by such 
agencies as cultivation, rodents, and surface washing of the soil. 
EFFECTS OF ROOTROT UPON THE WOODY TISSUES 
The effects upon the woody tissues of the roots are much less profound 
than upon the bark and are macroscopically evident as a uniform brown 
discoloration. In order to secure a better knowledge of the relation of 
the fungus to the wood, diseased'roots were embedded in celloidin, sec- 
Fig. i.—L ongitudinal section of a diseased apple root. The hyphae appear 
to traverse all of the xylem tissues equally well and in all directions. 
tioned, and stained. The hyphae appear to traverse all of the xylem 
tissues equally well and in all directions, as indicated in figure 1. They 
may follow the course of the vessel or medullary ray for some distance 
before diverging into adjacent cells. Perforation of the cell wall appears 
to be accomplished at any point, and no evidence has been noted that 
the pores serve as the places of passage. No considerable delignification 
occurs, as is shown by a comparison of normal and diseased wood when 
cross sections are treated with phloroglucin and hydrochloric acid. 
Starch very rapidly disappears, however, from invaded tissues, as is 
indicated by its absence when sections are tested with iodin. Confirma¬ 
tion of the digestion of starch by this fungus was secured by growth on 
starch agar. A halo extending beyond the margin of the colony resulted 
on this medium, thus affording an ocular demonstration of the excretion 
of amylase. Further evidence of the activity of this organism was 
