157 



and are then ready for market. Drying in the sun causes the rubber to become 

 sticky and should be strictly avoided. The trees are tapped four times a year ; 

 each time another side of the trunk is operated on. The yield each time is half a 

 pound of rubber, or one kilogram (2.2 pounds) in a year. I was informed that the 

 horizontal grooves male with the instrument described require only a quarter as 

 much time to fill up as the broad diagonal wounds made with the machete. The 

 former are completely closed in three months' time, and the tree recovers very 

 rapidly. 



Parkin's experiments in tapping Hevea in Ceylon gave results 

 much in favour of oblique incisions over either horizontal or ver- 

 tical. He says : 



In both cases the oblique incision yields about double that of the other. There 

 seems little difference between the amount collectible from a vertical and a hori- 

 zontal incision. Although there is a greater output of latex from the horizontal 

 cut, yet much more dries on the wound than in the case of the vertical, conse- 

 quently the amount which drops into the receiver comes to about the same in the 

 two cases.* 



With Hevea it was found that two oblique incisions joined be- 

 low to make a letter V gave nearly twice as much latex as one 

 alone. In case of Castilloa, however, where the milk flows so 

 much more freely, it was concluded that the most milk could be 

 secured with the least injury to the tree by means of separate 

 oblique incisions. Such cuts would certainly heal more readily 

 than V-shaped wounds, since the bark frequently receives its 

 worst injuries at the junction of the two incisions. 



TAPPING INSTRUMENTS. 

 That improved methods and tools are to be used for cultivated 

 trees is one of the points on which all the rubber planters agree, 

 but as yet none of the many improvements suggested has attained 

 any popularity, and it is at least doubtful whether any of the de- 

 vices brought forward at this time is to be looked upon as a prac- 

 tical solution of the problem. Some inventors have worked on 

 the erroneous idea that the rubber comes from the sap, like sugar 

 from the maple, and have thus completely wasted their time. 



An enumeration of some of the features essential for a good 

 tapping instrument may save further labour on wrong lines. 



The cutting edge must be keen, and must therefore be easy to 

 sharpen. A thick or blunt edge bruises the wood and milk tubes, 

 and this interferes with the flow of milk. 



There should be a means by which the depth of the cut can be 

 regulated, since it is important to cut deep enough to reach the 

 milk and yet not so deep as to reach into the wood, but axes and 

 chisels with shoulders to prevent too deep penetration are not 

 promising because the thickness of the outer bark is variable. 

 The shoulders also bruise the bark if the cutting is by blows. In 

 British India it is thought that the best instrument for tapping the 

 Para rubber trees is an ordinary carpenter's gouge. 



MULTIPLE TAPPING. 



By far the most important recent discovery in connection with 



the culture of Para rubber in the East Indies is what may be called 



multiple tapping, or the repeated cutting of the edges of the wound 



to induce a renewed flow of milk. This is, it is true, by no means 



♦Circular Royal Botanic Gardens, Ceylon, June, 1899, p. 121. 



