3 1 



ment with Fehling's Solution, to discover any considerable quantity 

 of reducing sugar in the zones of wood that were free from starch. 



It is obvious at the first glance, that this result corresponds 

 almost completely with the one I had previously obtained on 

 girdled trees : the reserve material disappears below the spot 

 operated upon, and accumulates above it. A wound extending 

 over the entire circumference of the stem, has therefore the 

 same effect as the girdling, because the rectilinear connection of 

 the conducting channels in the bark has been interrupted and 

 because the circulation of organic nutrient substances in an oblique 

 direction proceeds too slowly to provide the food supply required 

 by the base of the tree. 



Speaking generally, however, it seems to me that the conclu- 

 sion of most practical importance to us in our endeavour to 

 arrive at a decision on the various tapping methods is, that 

 after tapping qn the full spiral system, a sufficiency of the organic 

 nutrient substances that are necessary at the base of the tree for 

 the renewal of bark that has been removed, for the renewal 

 of the latex that has been extracted, for the normal growth in 

 girth of the tree, for the longitudinal growth of the roots and 

 for the respiration of the basal parts of the stem, cannot descend 

 there. The tree is therefore obliged to draw on the reserve 

 material from its reservoirs in the bark and wood. Tapping might 

 have been continued for quite a long time, as there was still a 

 sufficient quantity of tappable bark. During that time, the 

 reservoirs in the stem would certainly have been even more 

 completely emptied. 



Another point of practical importance for the determination 

 of the value of the various tapping methods is the fact, that a 

 certain amount of sap transport, though a slow one, is quite 

 possible in an oblique direction. I shall refer to this later on. 



Before doing so, however, I should like to report on a 

 second and final tapping experiment, which was commeneed 

 simultaneously with the first one. In this one, not the full .spiral 

 was adopted, but the half herring-bone system, which consists 

 in a number (six) of oblique cuts, one above the other. 

 The age of the tree was identical with that of the other 

 one, its girth was 50 cm. at the height of 1,00 in. Tin- 

 tapping cuts extended only over a quarter of the stem's 

 circumference. Their position on tin- tree, the distance between 



