54 



Where the disease is serious it will be found necessary to apply 

 a disinfectant to the tapped surfaces of every tree in the area. The 

 infection takes place on the cut. That is on the thin bark most 

 recently tapped. It is at this position then that the disinfectant 

 must be applied. The most important questions are the frequency 

 of application, the best disinfectant to use and the method most 

 practicable in estate practice. From an article in the most recent 

 Agricultural Bulletin I gather that in Sumatra it is found that the 

 best results are obtained if the disinfectant is applied every day. 

 From figures given in the article, by H. C, Pratt, to which I refer, 

 it appears that this is tlie only satisfactory method. The disinfectant 

 may be 20 per cent, carbolineum as used in Sumatra or its substitute 

 20 per cent, bi'unolinum, 10 per cent. Izal or a solution of sodium 

 bisulphite and formalin. The last question — the most practicable 

 method — may well be left for the planter to decide. 



BUBRS. 



These structures are too well-known to need any description. 

 Rutgers and Arens considered that they are produced as a result of 

 attacks of Phytophthora Faberi but there is no indication of the 

 presence of a fungus of any kind within the tissue of a burr or 

 nodule. 



Burrs are formed round a portion of a latex vessel as a result of 

 alteration of the contents of a latex vessel. Whether that alteration 

 bo disintegration, decomposition or coagulation, cortical cells sur- 

 rounding the latex vessel are stimulated to divide and form a 

 cambium which cuts off wood cells on its inner side forming a core of 

 wood tissue and bark cells on its outer side. The remains of 

 the latex vessel are easily discovered when sections are examined 

 microscopically. Similar nodules are produced as a result of latex 

 oozing out of a tube or occupying spaces between the cells (intercellular 

 spaces) or, occupying lesions in the cortex. Bryce divides these into 

 three types, he distinguishes yet another type which I have not 

 seen — namely, nodules which are formed round areas of cortex 

 from which latex may be entirely absent. 



I have not been able to iind any evidence whatever that this 

 pathological condition has any connection, directly or indirectly, 

 with the attack of any fungus disease or insect pest. 



Bryce suggests that " the tendency to suffer alteration in the 

 latex vessel content appears to be confined to certain individual 

 trees which have a predisposition to develop this condition." 



I think myself that in a very large proportion of the number 

 of burred trees the original centi^al point (round which the burr 

 develops) the factor which is the cause of the burr, is mei^ely 

 accidental, due to local coagulation or alteration of the latex within 

 the tube or' to the bursting of a tube allowing latex to occupy spaces 

 where it is foreign. 



