THE TAPPING OF RUBBER PLANTS 61 



die. The effect of thus " girdlmg " a tree represents the 

 maximum interference with the vital functions of the 

 plant which can be caused by tappmg, but all incisions 

 made in the bark will interrupt the transference of food- 

 substances in the plant to a greater or less degree, depend- 

 ing on the number, depth, and arrangement of the cuts. 

 The question therefore arises as to the extent to which 

 different tapping systems affect the vitality of the tree, 

 and whether the continued use of any method, adopted 

 probably without any regard for physiological considera- 

 tions, is likely to cause permanent damage to the trees, or 

 by depleting the food-supply mterfere with the formation 

 of fresh latex. This problem, which is of the highest 

 importance in comiection with the methods to be adopted 

 on rubber plantations, has been investigated, so far as 

 Hevea hrasiliejisis is concerned, by Professor Hans Fitting* 

 m Java, and his results have attracted considerable atten- 

 tion amongst rubber planters. 



Fitting's Researches. — It is not possible here to deal 

 in detail with Fitting's work, but a brief summary of his 

 experiments and conclusions may be given. He en- 

 deavoured to ascertain the probable effects of different 

 methods of tapping on the vitality of Para trees by in- 

 vestigating their influence on the reserve food-supply 

 stored in the tissues. He found that the effect of girdhng 

 Hevea trees was to cause an accumulation of reserve 

 food-material (starch) above the wound, whereas below 

 the wound the reserve supply of starch m the tissues 

 was very quicldy depleted in the case of young trees 

 and more slowly in older trees, the result in each case 

 bemg that a deficiency of food-material occurred sooner 

 or later at the base of the tree. A similar effect was 

 observed as the result of making an oblique spiral incision 

 extending over the entire circumference of the stem, 

 thereby interrupting the longitudinal course of the sieve- 

 tubes in the bark. In this case commmiication between 

 the bark above and below the incision is possible in an 

 oblique direction, but this is apparently not sufficient 

 to convey an adequate supply of fresh food-material from 

 above to the base of the tree. In a fiu-ther experiment 

 the haff-herringbone system of tapping, with six lateral 

 cuts, was employed, and the tapped area only extended 



* Beihefte zum Tropenpflanzer, 1909. 



