462 



Latex is very soon renewed after a period of tapping, but the pro- 

 duction of rubber (caoutchouc) is a very much slower one. Thus in 

 a trial of the spiral method of tapping on the largest tree in the 

 Garden (girth at 3 ft. from ground 9/ 4") we obtained from the first 

 period tapping 531 fluid ozs. of latex * giving 9 lbs. of rubber and from 

 the second period of tapping one month afterwards 433 ozs. of latex 

 giving only 4 lbs. 15 ozs of rubber (See Spiral Tapping) the ratios of 

 caoutchouc to latex comparing as 3 {-i fluid ounces to one ounce dry 

 rubber, as against 5 T 7 ^ fluid ozs. to the same amount of rubber. It is 

 therefore of the greatest importance to the cultivator in tapping to 

 avoid tapping at the wrong season when he is very liable to interfere 

 with the special physiological processes in the tree then performing 

 their functions. The periods of these processes cannot be controlled 

 or modified, the cultivator will therefore have to adapt his work so 

 as not to clash with them. The bark of the tree does not recover as 

 well from wounds during the resting period between December and 

 March, nor does it appear that the return of caoutchouc is as good. 

 Further experiments we hope to carry out next year on this most 

 important subject which will probably furnish the key to the whole 

 of the rationale of the rubber industry. Rapid and good renewal of 

 the bark is very necessary not only to protect the wound from in- 

 jurious attacks of fungi but to increase the production of caoutchouc. 

 Too frequent or prolonged tapping is not only injurious but pro- 

 duces a latex verj' inferior in its rubber-producing qualities. This can 

 only be due to actual bark injury. The experiments made on an old 

 stump in the Botanic Gardens seem to show this and to throw some 

 light on the origin of rubber in the plant. A figure of this stump is 

 given herewith. It was a tree of considerable size, measuring 40 

 inches in girth at three feet from the ground when the top was 

 broken off accidentally some ten years ago. It then commenced to 

 die from the top and till a few years ago produced at intervals 

 shoots bearing a few leaves, the remains of the last of which can be 

 seen just above the Polyporus fructification growing on the decay- 

 ing wood. It had by this year died down to within two feet of the 

 ground and was tapped by single incisions at the base, from which 

 were obtained 3J oz. of dry, and very strong rubber. The bark was 

 renewed in a few months, and was again found to contain rubber. It 

 is long since there have been any leaves on the tree and it is clear that 

 only the bark and roots have played any part in the renewal of the 

 latex in the stump. 



The experiments made this year show that although in over-tap- 

 ping latex is renewed in the bark quickly, caoutchouc takes much 

 longer to produce, though it does not seem in the worst cases ever 

 to be entirely absent from the latex. The caoutchouc seems un- 

 doubtedly to be directly or indirectly produced from the roots, but 

 as the only injury to the tree in tapping is caused to the bark of the 

 trunk it seems clear that it is the bark injury only which reduces 

 the amount of caoutchouc in the latex for it does not seem probable 

 that the roots can be affected by the bark injury. 



* Including the same quantity of added water at each period. 



