METHODS OF MAKING INCISIONS. 67 



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 made 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 favor of oblique incisions over either horizontal or vertical. 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 horizon- 

 tal 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, consequently the 

 amount which drops into the receiver comes to about the same in the two cases. a 



With Hevea it was found that two oblique incisions joined below to 

 make a letter V gave nearly twice as much latex as one alone. In case 

 of Castilla, 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 cer- 

 tainly heal more readily than V-shaped wounds, since the bark fre- 

 quently 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 devices brought forward 

 at this time is to be looked upon as a practical 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 com- 

 pletely wasted their time. 



An enumeration of some of the features essential for a good tapping 

 instrument may save further labor 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 regu- 

 lated, 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 ordi- 

 nary carpenter's gouge. 



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



