May, 1910,1 



387 



GUMS, RESINS, SAPS AND EXUDATIONS. 



THE SCIENCE AND PRACTICE OF 

 PARA RUBBER CULTIVATION. 



By John Parkin, m.a., f.l.s, 



(Prom Science Progress, No. 15, 

 January, 1910.) 



{Continued from p. 296.) 



Part II. 



The Extraction of thb Latex. 



The procedure employed in the East 

 for the extraction of the latex from the 

 stems of cultivated Hevea trees was 

 elaborated independently, and not in- 

 fluenced by the native method still used 

 in the forests of the Amazon. 



The late Dr. Trimen in 1888 commenced 

 tapping experiments at Henei atgoda in 

 Ceylon on the rubber trees which had 

 grown from the seedlings received from 

 Kewiu 1876. Vertical vows of V-shaped 

 incisions were made in the bark of the 

 trunk, from a height of six feet down- 

 wards, with a mallet aud carpenter's 

 chisel. The incisions were placed about 

 a foot apart vertically, and the rows at 

 a like distance horizontally, The latex 

 oozing out of these cuts was made to 

 trickle down the surface of the bark in a 

 series of streams corresponding to the 

 number of vertical rows of incisions. 

 The whole of the milk was caught at the 

 base by a clay gutter moulded round 

 the trunk, and directed into one or more 

 coconut shells placed around the foot of 

 the tree. A second tapping was per- 

 formed in a similar manner, the new 

 incisions being inserted between the old 

 ones, and so for subsequent bleedings. 

 For details of this somewhat crude 

 method, now almost obsolete, the reader 

 is referred to one of the circulars 

 published by the Ceylon Botanic Gardens 

 Department.* 



Dr. Willis continued the tapping ex- 

 periments initiated by his predecessor, 

 employing the same method. His results 

 with respect to yield of rubber per siugle 

 tapping brought out the remarkable fact 

 that the second tapping gives a consider- 

 ably larger quantity of caoutchouc than 

 the first. Since his figures gave the 

 first indication of the now well-known 

 " wound-response," it may be of interest 

 to quote his remarks and figures from 

 the circulart already referred to :— 



* Willis, Circular, Royal Botanic Gardens, 

 Ceylon, 1898, No. 4, Series I. 20,31 



t Willis, Circular, Royal Botanic Gardens, 

 Ceylon, 1898, No. i, Series I. p, 32 



"The tappings may follow one another 

 at intervals of a week for about four to 

 eight weeks, The second tapping gives 

 a much larger yield than the first, and 

 the third and fourth tappings are 

 usually very productive. In a series of 

 experiments made during 1897 on trees 

 of about two feet mean girth, the 

 average yield per tree of the successive 

 weekly tappings was as follows : — 



oz. 



First week '73 



Second week 1*48 



Third week '97 



Fourth week '80 



Fifth week -67 



Sixth week '52 



Total 5'17 " 



Willis, realising that the methods he 

 was then ufing for the extraction and 

 preparation of the rubber were probably 

 capable of much improvement, set the 

 writer (who had just been appointed his 

 scientific assistant) to work on these 

 matters. The main outcome of this 

 investigation,* carried out in Ceylon 

 at both Peradeniya and Heneratgoda 

 in 1898-99, consisted in the demonstration 

 of "wound-response" and the intro- 

 duction of an easy means of preparing 

 rubber of high quality and purity from 

 the latex. The subject of preparation ia 

 treated of in the next section of this 

 paper. Our attention must now be 

 turned to the phenomenon of wound 

 response. 



Wound-re aponse. — On general grounds 

 it might be assumed that the trunk of a 

 rubber tree would have yielded most of 

 its store of latex after a single extensive 

 tapping, so that none, or very little, 

 would be forthcoming from a second 

 tapping within a few days. This is 

 practically what happens in the case of 

 Castilloa elaslica. 



On the other hand, taking into account 

 Willis's results, which show about double 

 the weight of rubber from the second 

 tapping, it might be conjectured that 

 the injuries (incisions) stimulated in some 

 way the accumulation of latex, so that 

 a greater flow would issue from a similar 

 number of incisions made a few days 

 later. This, in fact, is how Hevea 

 behaves. 



Several simple experiments soon proved 

 this. One was conducted in this wise. 

 A piece of bark about an inch square 

 was removed from certain Hevea trunks. 



* J. Parkin, Circular, Royal Botanic Gardens p 

 Ceylon, 1899, Nos, 12, 13, 14, Series I, 



