26 



summed up as follows : Corresponding with the absence of medul- 

 lary bast , a severance of the bast and the cortex will completely 

 interrupt the downward current of organic food material, so that 

 the reservoirs in the stem below the place of severance will, in 

 the case of young trees, be very soon emptied, in that of older 

 ones, more slowly. The result of this will be that a deficiency of 

 food will sooner or later occur in the base of the tree. 



It would ihave been of great interest, not only for our 

 immediate purpose, but also in its relation to the tapping problem, 

 to ascertain by experiment, how rapidly the reservoirs which had 

 been emptied completely by girdling, would be refilled, when 

 the connections between the severed portions of the bark have 

 been re-established, as for instance, by the joining together of 

 the wound-calli. Such experiments would, however, have required 

 more trees for experimental purposes and more time than I had 

 at my disposal. 



B. Influence of the Tapping Incisions on the Distribution and 

 Circulation of Sap in the Stem of Hevea. 



In order to be able to compare in the easiest possible manner, 

 the influence exercised on the circulation of sap 'by the various 

 tapping cuts, with that of complete girdling, we must first consider 

 those tapping systems in which the rectilinear connection of the 

 channels for the organic substances is interrupted round the 

 whole girth of the stem, as in the case of girdling. These systems 

 only differ essentially from the ordinary method of girdling by 

 permitting a circulation of sap in an oblique direction, and also 

 because possibly the innermost channels in the bast, the youngest 

 and those nearest the cambium, can still be utilised for conveying 

 feed. Piobably the simplest of these systems is the English full 

 spiral system. It was very much in vogue some time ago, and 

 probably is still very popular. [The full-spiral system was recom- 

 mended in Ceylon at one time, and experiments were made at the 

 Heneratgoda Government plantation; but the recommendation 

 was never widely adopted, either in Ceylon or the Malay 

 Peninsula, and was speedily abandoned. Tr.] A spiral curve is 

 cut in a slanting direction in the bark, beginning at about the 

 height of a man, and continuing down to the base of the stem. 

 The incision is carried one and a half to three times or more 



