oz 

 First week . . . "73 



Second week . . . 1*48 

 Third week . . . "97 



PARA-RUBBER CULTIVATION 405 



" wound-response," it may be of interest to quote his remarks 

 and figures from the circular ] already referred to : 



" 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 experi- 

 ments 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. 



Fourth week . . . '80 

 Fifth week . . . '67 



Sixth week . . '52 



Total . 517 oz." 



Willis, realising that the methods he was then using 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, 2 carried out in Ceylon 

 at both Peradeniya and Henaratgoda in 1898-99, consisted in 

 the demonstration of " wound-response," and the introduction 

 of an easy means of preparing rubber of high quality and 

 purity from the latex. The subject of preparation is treated 

 of in the next section of this paper. Our attention must now 

 be turned to the phenomenon of wound-response. 



Wound-response. — 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 elastica. 



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 con- 

 ducted in this wise. A piece of bark about an inch square was 



1 Willis, Circular, Roy. Rot. Gardens, Ceylon, 1898, No. 4, Series I. p. 32. 



2 J. Parkin, Circulars, Roy. Rot. Gardens, Ceylon, 1899, Nos. 12, 13, 14, 

 Series I. 



