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to the falling off in quantity and quality of latex, after repeated 

 tapping operations, performed by very extensive incisions. 



And lastly there is another question to which I must draw 

 attention, and which cropped up during my experiments, namely: 

 How long a time will elapse before starch can again be stored in 

 the bark that has been renewed on the tapping wounds. I have 

 never in my experiments noticed a storage of starch in bark 

 that had been renewed on the tapping spots, not even when a 

 sufficient quantity of food material had been procurable from 

 the neighbourhood, even when, after tapping operations, the bark 

 had had four to five months time to ripen. This accords with the 

 extraordinary fact, that starch is not stored in the calli formed 

 as the result of girdling, not even on the upper edge of the 

 incision, where organic material accumulates largely in the bark 

 next to the callus. The result of an examination of a very old 

 callus, is of great interest in this connection, because it proved 

 that a long period of time can elapse without any storage 

 of starch taking place in calli of this description. In the Large 

 Botanic Garden at Buitenzorg, I came across an 1 8-year-old 

 Hevea tree, the circumference of which was 75 cm, at the height 

 of a man's chest, and which had been tapped in February, 1907, 

 by a spiral curve cutting down to the wood. On the upper and 

 lower edges of the wound, calli had been formed. In a piece 

 of callus which I excised on December 22nd, I found no starch, 

 neither was there any in the new wood formed just beneath it, 

 while a quantity of starch was contained in the old bark just 

 above it. Nor did I find any special quantities of reducing sugar 

 in the callus. In order, therefore, to find out the condition of the 

 tree at the time when a second tapping period is to succeed the 

 first one, it would certainly be very important to ascertain whether 

 the newly-formed bark has regained its power of storing starch 

 or not. 



It is evident that there are many important questions which 

 arise in connection with my experiments, and all of them questions 

 to which an answer can be found as rapidly and easily as possible 

 by an investigation of the distribution of material (of starch 

 especially), if only there are sufficient plants at one's disposal. 

 That was not so in my case. But I should imagine that in a 

 country, rich in rubber plantations, it ought not to be difficult to 

 induce planters to devote some trees to experimental purposes 



