May, 1910. j 



391 



Saps and Exudations, 



antly. Here there is surplus of 

 moisture in the soil, and so the tubes are 

 always well distended with latex. There 

 is, in fact, no need to draw upon this 

 reserve. 



The removal of latex from the Para- 

 rubber tree appears to have little or 

 no detrimental effect. A young tree 

 judiciously tapped continues to grow 

 almost as well as one which has not been 

 touched. Some observations made by 

 Macmillan and Petch* have shown, 

 however, that the seeds from tapped 

 trees are, on the whole, lighter in weight 

 than those from untapped ones. Any 

 prejudicial effect of the tapping is 

 probably due rather to the injury to and 

 removal of the surrounding tissues than 

 to the extraction of the latex itself. 



Tapping Systems. -The demonstration 

 of wound-response quickly influenced 

 the method of tapping Hevea trees 

 followed in the Bast. To gain the full 

 benefit of this response, the new incision 

 must be made quite near the previous 

 one. Thus was suggested the feasibility 

 of re-opening the old wound, rather than 

 of making a fresh incision. Experience 

 has shown that very satisfactory results 

 can be so obtained. A thin paring of 

 bark is removed from the lower edge of 

 the initial groove at each subsequent 

 tapping. By this means the bark down 

 to the cambium is gradually shaved 

 away. Thus excision instead of incision 

 has come to control the tapping systems 

 now in vogue. 



The original small V-shaped cut has 

 been completely abandoned. Attention 

 to wound-response showed that a single 

 slanting cut served just as well. Oblique 

 incisions form the basis of the methods 

 of tapping in use. 



At first the latex from each incision 

 was collected separately. This involves 

 more labour, and has been generally dis- 

 carded for basal collection. 



The two chief systems of tapping now 

 practised on the estate are those known 

 as the Spiral and the Herring-bone. The 

 principle is the same in buth. The 

 initial grooviug (tapping) forms a guide 

 for all subsequent tappings performed 

 during the year. 



Spiral System. — A spiral groove is 

 made in the bark of the trunk from a 

 height of six feet to the base. If the 

 incision is carried completely round the 

 stem, then the system is called the Pull 

 Spiral ; if only one part way round, the 

 Half Spiral. A bole of small girth will 

 only require one spiral. If of larger 



* Mtcniilhn and Petch, Circular, Royal Bo- 

 tanic Gardens, Ceylon, 1908, Vol. iv, No. 11, 



circumference, then an extra spiral can 

 be added for each additional foot of 

 girth ; thus a tree three feet round 

 would need three. At each tapping a thin 

 shaving of bark is removed from the 

 lower edge of the spiral cut. The 

 pressure of latex is thereby relieved and 

 a stream flows down the spiral into the 

 receptacle placed at the base. 



The full spiral, of all methods of tap- 

 ping, yields the largest quantity of 

 rubber in a given time, but it is very 

 drastic, as the whole of the cortical 

 tissues from the height of six feet down- 

 wards is removed, most likely too quickly 

 for the maintenance of the tree's general 

 health. It is now considered the best 

 system to adopt for trees which are 

 subsequently to be removed as thinnings 

 or for other reasons. Rubber in quantity 

 is thus obtained with the minimum 

 amount of labour. 



Herring-bone System. — A vertical 

 groove is made in the bark }f the trunk 

 extendiugfrom the base toaheight of five 

 or six feet. Then long oblique incisions 

 about a foot apart are cut from it in an 

 upward slanting direction. If the in- 

 clined cuts are made alternately on each 

 side of the vertical groove, the method 

 is known as the Full Herring-bone; if 

 only on one side, the Half Herring- 

 bone, thus: 



/ 



Full 

 Herring- 

 bone. 



Half 

 Herring- 

 bone. 



The oblique iacisious yield the latex, 

 and the vertical groove serves as a 

 channel of conduction to the basal recep- 

 tacle. At each subsequent tapping a 

 thin paring is taken off the lowei edge 

 of each oblique cut ; the vertical groove 

 is left untouched. Thus the extraction 

 of latex from the area of trunk covered 

 by the herring-bone can be continued, 

 till the whole of the bark intervening 

 between the origiual slanting incisions 

 has been excised. 



The half herring-bone is now generally 

 preferred, as being less severe than the 

 full herring-bone. A quarter of the 

 girth of the trunk can be tapped on the 

 former system each year. By the time 

 (four years) the whole has been so 



