RUBBER PLANTING 193 



show that they appear in greater numbers on trees 

 which have been tapped with a pricking instrument 

 than on trees which have only been pared. In fact, the 

 whole subject of their origin seems to require further 

 investigation. 



The nodules arise as minute woody bodies buried 

 in the growing bark, quite independently of the proper 

 wood of the tree. Their presence is first betrayed by a 

 swelling and cracking of the outer bark. If the surface 

 of such a swelling is sliced off with a sharp knife, 

 numerous nodules, about the size of small peas, are 

 found embedded in the bark. At this stage they may 

 be carefully extracted with the point of a knife, and if 

 this extraction is carried out with thoroughness the bark 

 recovers and no further injury is done. If neglected, 

 however, the nodules grow with great rapidity, and fuse 

 with one another and with the actual wood of the tree. 

 The surface of the tree now shows extensive rugged 

 prominences over which tapping by the ordinary process 

 of paring is no longer possible. The woody mass may 

 still be prized off with a hatchet or a crow-bar, but 

 a ragged and extensive wound is left which takes a long 

 time to heal. 



At certain seasons these nodules have appeared on 

 large numbers of trees all over Ceylon. At other times 

 their appearance may pass almost unrecorded for years 

 together. It was observed that the worst visitation 

 occurred after a prolonged period of drought, and was 

 most severe at high elevations and on trees which had 

 L, 13 



