HEART-ROT 117 
which the trees have been attacked, whilst those with 
secondary rot have been attacked in a reverse direction, 
i.e. from the trunk. For the rot on entering the trunk 
will spread in all directions in the heart-wood, and will 
grow as much down the roots as it does up the stem. The 
fact that secondary rot occurs in this way was established 
by finding that in such roots the rot at no point reaches 
the surface, so that it is clear that the disease cannot have 
entered by them (sec fig. 37). 
It is among the roots with primary rot, then, that we 
must look for the source of infection. And these roots 
show a very marked localization. In all the roots of the 
pumped trees I only found one superficial root which showed 
primary rot; all the other roots in this stage had grown 
more or less vertically downwards into the subsoil, and 
were situated almost directly underneath the trunk itself. 
In eight of the trees a tap-root, or other root which had 
early taken its place, could be distinguished, and in every 
case but one this root showed primary rot. In two of these 
trees no other root was in the same state, in one tree one 
other root was, in three two other roots, in one four others, 
and in one six others. In the tree in which the tap-root 
did not show primary rot, two others did, and two trees in 
which no tap-root could be found had respectively six and 
seven roots showing primary rot. Thus in all thirty-four 
roots were found with primary rot, and only one of these 
could possibly be called a superficial root. When the trees 
were uprooted the surface roots were firm and spread out 
from the tree in the usual way, though most of them were 
rotted in the core, and the wholly rotted roots had to be 
sought on the under-side, where they were usually broken 
off short. Their position could generally be located in the 
soil from which the trees had been raised, and they could 
be seen to continue in their vertical or nearly vertical 
course. The conclusion is unavoidable that the trees were 
rotted either through their tap-roots or through their deep- 
going ‘ anchor ’ roots and not through the spreading super- 
ficial roots. Similar evidence has been forthcoming in trees 
