118 HEART-ROT 



from other woods. A rootstock sent me from Tinterii 

 showed the same phenomenon, and a wind-blown larch on 

 the Endsleigh estate had been rotted solely through its 

 tap-root. 



We are thus confronted with the fact that the disease 

 enters the trees through roots either the tap-root or 

 ' anchor ' roots which grow more or less vertically down- 

 wards and penetrate the subsoil. With this in view I had 

 a trench cut 3 ft. deep in order to ascertain the state of 

 the roots in the subsoil. The superficial 9 in. of soil was 

 composed of blackish-brown humus and loam. For the 

 next 14 in. there was a fairly loose sand with broken ' grey- 

 stone ', and it contained numerous healthy roots of larch 

 and oak. Below this to the lowest point reached in digging 

 the sand was tenacious, and bound as though with an 

 admixture of clay, and contained numerous stones. There 

 were few roots in this layer, and many of those which 

 I picked out were dead. In fact I estimated that in the 

 hard subsoil 60 per cent, of the larch roots and 25 per cent, 

 of the oak roots had been killed, though a few of them were 

 rotted. This wood a mixture of larch and oak was 

 54 years old. For comparison I had a similar trench cut 

 in a pure oak wood alongside which was 105 years old. 

 The soil was here composed of a superficial 3 in. of black 

 leaf -mould and 18 in. of a sandy loam with a few stones 

 and very many healthy oak roots. At 21 in. (the same 

 depth as in the former trench) the sand became much more 

 compact, but not nearly so hard as in the younger wood. 

 There were a few oak roots, all of which were vigorous. 



The points that chiefly interest us in comparing the two 

 trenches are, firstly, that in the older wood the subsoil is 

 much looser and more broken up than in the younger wood, 

 and, secondly, that many of the subsoil roots were dead 

 in the younger wood, whereas all were alive in the older 

 wood. The cause of death in the former case is almost 

 certainly lack of air, for, like all other parts of plants, roots 

 must have access to a supply of free oxygen in order to 

 maintain their vitality. 



