RUBBER 605 



be applied to trees in tapping. It has been recently 

 stated that there is no reason why Bordeaux mixture 

 should be recommended, since lime-sulphur mixture is 

 free from that objection and equally serviceable. 



But the results cf all experimental work available prove 

 that lime-sulphur mixture is not toxic to Phytophthora, 

 Whether the Phytophthora Faberi will prove an excep- 

 tion remains to be demonstrated. Experiments in spray- 

 ing with Bordeaux mixture were carried out on twenty- 

 rive trees at Peradeniya, the rubber subsequently collected 

 being made up in biscuits. The amount of copper in the 

 biscuits made immediately after the spraying was very 

 small, and none of the biscuits made during the next six 

 months turned tacky. It is intended to repeat this experi- 

 ment, and it is hoped that other experiment stations will 

 do the same. 



Almost as serious as canker from the tapping stand- 

 point is the formation of nodules or burrs on the stem. 

 As far as is known at present, these are not attributable 

 to either insect or fungus agency. They occur on un- 

 tapped as well as on tapped trees, and are most numerous 

 on trees which have been tapped with a pricker. The 

 lower part of the stem may become thickly covered 

 with large excrescences, so that any regular tapping is 

 impossible. 



The commonest form of nodule in Ceylon begins as a 

 small sphere or cylinder of wood in the middle of the 

 cortex. Its nucleus consists of a small group of brown 

 cells. A cambium, quite distinct from the main cambium 

 of the stem, develops round this group of cells, and then 

 proceeds to build wood round them. As the nodule 

 increases in size it develops points directed inwards, which 

 ultimately unite with the main wood of the stem. These 

 nodules are easily removed when they are small before 

 they have become united to the main wood. 



If several of these nodules arise close together they 

 may fuse and form a plate. But the formation of plates 

 often takes place in a different manner. Instead of a 

 group, more or less spherical or cylindrical, of brown 

 cells, the nucleus of a plate is a sheet of such. These 

 sheets may occasionally be met with in the middle of 



