August, 1910.J 



101 



Saps' and Exudations. 



were not available until September, 

 agree with those of the first period and 

 support his conclusion. 



Analysis of the figures, however, 

 throws some doubt on the results arrived 

 at. Working out the yield per tree per 

 tapping, we have the following figures 

 (in ounces) : — 



A. B. C. 



First period. 

 0-88 0-55 78 



Second period. 

 0-65 0-40 0-88 



Third period. 

 0-22 0-30 0-05 



For the first 37 tappings, A yields *88 

 ounces per tree per tapping ; for the 

 next 20 tappings it yields '65 ounces per 

 tree per tapping, and for the last 34 

 tappings, it yields "22 ounces per tree 

 per tapping. B follows a similar course. 

 But O, after yielding "78 ounces per tree 

 per tapping for 39 tappings, rises to "88 

 ounces per tree per tapping for the next 18 

 tappings, and then falls to "05 ounces per 

 tree per tapping for the last 35 tappings. 

 Such a result is quite anomalous ; but, 

 unfortunately, it is obtained in experi- 

 ments 2 and 3 in just the two groups 

 which have the most important bearing 

 upon the point under experiment. As it 

 stands, this result is inexplicable. The 

 rise in the second period cannot be attri- 

 buted to the effect of wound reponse, 

 since it follows 39 tappings. Nor can the 

 low yield of the last 35 tappings be put 

 down to exhaustion ; for the total 

 number of tappings is only 92, the trees 

 were only tapped twice per week, and 

 only 3 to 4 inches of bark had been 

 removed (Wright, T.A., December, 1906). 

 Nor is it to be attributed to the individual 

 peculiarity of the trees, for it is not the 

 yield of one tree but the average of 25. 



To tap 25 trees, 15 to 20 years old, 

 35 times (i.e., for 17 weeks), and obtain 

 only 3 lbs. of rubber must constitute a 

 record. But it seems fairly evident that 

 the figures for are questionable. If 

 they are correct, then the full herring 

 bone is the most exhaustive method of 

 tapping, for after 57 tappings the trees 

 yield practically nothing. 



Wright concludes that the full spiral 

 is the best method to adopt in thinning 

 out estates which are too thickly 

 planted, since it removes the maximum 

 quantity of bark in a given time. *But 

 it does not follow, even if we accept the 

 results quoted above, that it yields the 

 greatest amount of rubber. In the 

 experiments quoted, the full spiral 

 yielded 82 3/16 lbs. of rubber, while the 

 full herring bone yielded 75 lbs. But 

 the full spiral tapped right round the 



tree, while the herring bone dealt only 

 with one side (Wright, T. A., December, 

 1906). It would be possible, therefore, if 

 it were desired to injure the tree, to put 

 another herring bone, perhaps smaller, 

 on the other side ; and a small yield from 

 the second herring bone would suffice to 

 make that method the better. It may 

 be noted that, as appears further in 

 experiment 3, the total yields per tree of 

 A, B, and C are remarkably low in com- 

 parison with the other groups. 



Experiment 3. 



To Determine the Yield obtainable 

 by Tapping at Different Intervals^ 

 Four groups of trees were selected for 

 this experiment, and another (A) was 

 subsequently added. All were tapped by 

 the full spiral, up to 5 ft. or 5 ft. 6," From 

 the figures it would appear that the trees 

 of group A differed considerably from 

 the remainder. The groups were :— 



Number of trees, Tapped. 



D ... 5 ... every day 



E ... 5 ... every other day 



A ... 25 ... twice per week 



F ... 5 ... once per week 



G ... 5 ... once per month. 



In D and B, Sundays are not reckon- 

 ed, so that the trees were tapped six 

 times and three times per week res- 

 pectively. The results to September, 

 1906, are :— 



Yield per tree 



No. of tappings. in lbs. 



D ... 270 ... 11-0 



E ... 136 ... 12-5 



A ... 91 ... 33 



F ... 44 ... 3-8 



G ... 11 ... 0-625 



F appears to have missed one tapping, 

 while E and A each received one extra. 



These figures apparently prove most 

 conclusively that tapping every altern- 

 ate day yields more in a given time 

 than tapping every day. As a rule it is 

 considered that alternate day tapping 

 halves the labour, but gives less rubber 

 than every day tapping, the gain being 

 in the labour per lb. of rubber obtained. 

 But in this case, not only is the labour 

 halved, but the yield per tapping is 

 more than doubled. Nothing could be 

 more conclusive until the figures are 

 analysed. 



Calculating the yield per tree per tap- 

 ping (in ounces) we find that D gave '(35 

 oz. ; E, 147 oz. ; A, -58 oz. ; F, 1 '38 oz. ; and G, 

 ■91 oz. G may be left out, as the group 

 was only tapped eleven times, and there 

 could be very little " wound response" ; 

 practically each tapping was an inde- 

 pendent tapping ; t ie last four tappings, 



