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 (see 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 



