FORESTEY. 47 



Hevea rubber cultivation and curing at Non Pareil Estate, Sangre Grande, 

 Trinidad, E. A. Robinson and J. W. Sargeant (Bui. Dept. Agr. Trinidad and 

 Tohago, 14 {1915), No. 4, PP- H^, 119). — Tapping experiments conducted witli 

 1,200 6- to 9-year-old Hevea trees for tlie season of 1914-15 resulted in a yield 

 of 1,608 lbs. of rubber, or a gross return of $147 per acre with the rubber at 

 50 cts. per pound. The cost of cultivation, manufacture, and sale of this rubber 

 was $86.14, leaving a net profit of $60.86 per acre. 



Physiological effects produced on Hevea brasiliensis by various tapping 

 systems, L. E. Campbell {Dept. Agr. Ceylon Bui. 19 {1915), pp. 27). — Bulletin 

 12 of this series (E. S. R., 33, p. 542) gave the yield secured from various sys- 

 tems of tapping. The present bulletin contains the re.sults of examinations of 

 the trees included in the tapping experiments with regard to the relative quan- 

 tities of reserve food stored in the bark and wood in and at various distances 

 from the tapped areas. 



Of six systems of tapping examined, four had an entirely local effect on the 

 reserve food supplies of the trees. In the remaining cases other than local 

 effects were apparent. Reserves of starch had been withdrawn from large 

 regions below the tapped area, and there were also indications that the effects 

 extended even to the roots. 



A comparison of different methods of knife tapping and the pricking methods 

 of tapping shows that the effects produced on the local food storage by the 

 pricking methods have been no less drastic than those resulting from ordinary 

 knife cuts. In the majority of cases the effects have been considerably more 

 marked. The untapped bark between the incisions was very poor and some- 

 times completely deficient in reserve starch. These effects are attributed largely 

 to the formation of wound-wood, which not only required a large amount of 

 reserve material for its formation but also hindered the lateral transference of 

 reserve material across it. With the pricking method of tapping the percentage 

 of scrap in the total yield of rubber was very high. 



The effect of different intervals between successive tappings of Hevea 

 brasiliensis, T. Fetch {Dept. Agr. Ceylon Bui. 20 {1915), pp. 26). — In connec- 

 tion with tapping experiments of Hevea trees conducted at Henaratgoda (E. S. 

 R., 33, p. 543), observations were made of the effects of tapping at various 

 intervals of from one up to nine days between the tappings. 



Although the results are not conclusive they indicate that within limits the 

 yield per tapping increases as the time interval between tcippings is increased. 

 The greatest yield in a given time is obtained by tapping at the shortest interval 

 within the limits under experiment. With the longer tapping interval the num- 

 ber of cuts whch it is possible to make to an inch decreases up to an interval of 

 about five days, but this decrease does not nullify the increase in yield per tap- 

 ping. The yield per unit of bark excised increases as the tapping interval is 

 lengthened, at least up to an interval of about six days. After five years' con- 

 tinuous tapping there is no evidence that the yield obtained in a given time by 

 tapping at an interval of five or seven days will ultimately exceed that obtained 

 by more frequent tapping. 



Dynamite experiments, B. Bunting {Agr. Bui. Fed. Malay States, 3 {1915), 

 No. 9, pp. 337-341). — Experiments were conducted at the Castleton Estate, Telok 

 Anson, to test the effect of explosives on the growth of rubber. As measured 

 by the girth increment for one year the control plat gave an average increase in 

 girth of 21.93 per cent, and the dynamite plat an increase of 32.14 per cent for 

 every 100 in. of the original girth. 



Summing up the results of various exioeriments with dynamite conducted by 

 the Department of Agriculture in the Federated Malay States, it appears to be 

 unequaled for breaking up hardpan. It is most effective on heavy clay and 



