July, 1909. 



5 



Saps and Exudations. 



theie often arises an abnormal growth 

 of woody nodules in the bark itself, 

 as has been fully described by Mr. Fetch 

 in a recent circular (Vol. IV., No. 18). 

 These nodules lead to serious difficul- 

 ties in the tapping of the renewed bark. 

 Mr. Petch associates this form of injury 

 especially with the use of the blunt 

 pricker, although we are assuied that 

 this instrument has frequently been 

 used without the production of any of 

 these nodules. The precise effect no 

 doubt depends to a considerable extent 

 upon the individuality and vigour of 

 particular groups of trees. At the 

 present time we do not consider that 

 the problem of what is the best possible 

 method of tapping is by any means 

 settled, and whilst recommending that 

 every new method should receive a 

 thorough and extensive trial, we are 

 inclined on purely theoretical grounds 

 to adopt a somewhat conservative atti- 

 tude, believing that the greatest safety 

 lies in careful paring by the herring- 

 bone or half-herring-bone method. In 

 operating this method not more than a 

 third of the circumference of the tree 

 should be attacked at any one time. 



RUBBER CULTURE IN CEYLON. 



(From the Gardeners' Chronicle, XLV., 

 1, 151, January, 1909.) 



Attention was drawn in our issue of 

 October 3rd last, to the developments 

 which have taken place during recent 

 years in the cultivation of rubber plants. 

 It was pointed out how largely these 

 developments have been due to the 

 activities of the Government Botanic 

 Departments in various parts of the 

 world. Although the cultivation of 

 Rubber is being prosecuted with zeal in 

 the tropical possessions of other nations, 

 it is gratifying to be able to record that 

 the pioneer work was carried on within 

 the British Empire. The first important 

 step was the introduction to Ceylon 

 and elsewhere of the supplies collected 

 by Mr. H. A. Wickham in the Amazon 

 v alley and brought to Kew under cir- 

 cumstances of considerable difficulty. 

 The expense of Mr. Wickham's expedi- 

 tion was borne by the Government of 

 India, but, as Ceylon seemed to offer 

 more suitable condition^, the young 

 plants were despatched^ thither, and 

 later this colony acted as the distribut- 

 ing centre for other British possessions. 

 The staff of the Ceylon Botanic Gardens, 

 moreover, carried out experimental 

 work and made discoveries which were, 

 in a large measure, instrumental in 

 securing for rubber cultivation the 

 position of a profitable industry. 



The world's annual output of rubber 

 is now about 69,000 tons, of which amount 

 tropical America contributes some 64 

 per cent., tropical Africa 34 per cent,, 

 and tropical Asia the remaining 2 per 

 cent. The tropical American yield is 

 credited in the main to three plants, 

 Hevea brasiliensis (Para rubber), Mani 

 hot Glaziovii (Ceara rubber), and Castil- 

 loa elastica (Central American rubber). 

 Other species of Hevea and various 

 species of the allied genus Sapium pro- 

 bably also contribute to the output of 

 " Para rubber." More than one species 

 of rubber-producing Castilloa have also 

 been recognised, and recent observa- 

 tions point to there being other useful 

 species of Manihot besides M. Galziovii. 

 The three plants mentioned may, how- 

 ever, be regarded as being the main 

 source of American rubber. They have 

 all been introduced into Ceylon, and we 

 may consider separately their histories 

 in the colony. 



Of Hevea brasiliensis, a supply of 

 some 2,000 young plants was received 

 in Ceylon in 1876, transmitted from 

 Kew in thirty-nine Wardian cases. 

 These plants had been raised from the 

 seed collected by Mr. Wickham in the 

 Amazon Valley. A special garden was 

 prepared for their reception at Hena- 

 ratgoda in the low, moist country, 

 and some were also planted at Pera- 

 deuiya, about 1,500 feet elevation. 

 The plants succeeded very well. Hena- 

 ratgoda soon supplied plants to widely 

 distant parts of the tropics, at first 

 from cuttings and later from seed, 

 As the plants became old enough to 

 yield rubber— usually about their sixth 

 year— experimental tappings were com- 

 menced. To this end V-shaped incisions 

 were made in the bark of' the young 

 trees, and the exuding latex collected 

 in cups of coconut shell placed at the 

 base of each trunk. In this manner the 

 late Dr. Trimen, f.r.s., the then Director 

 of the Gardens, obtained from one tree, 

 during six years, by tapping made in 

 1888, 1890, 1892, and 1894, a yield of over 

 10h lbs. of good dry rubber. A definite 

 step forward resulted from the experi- 

 mental work of Dr. J. C. Willis, the 

 present Director of the Ceylon Botanical 

 Gardens, and Mr. J. C. Parkin, who 

 carried out the investigations from 1897 

 onwards. They discovered the existence 

 of the phenomenon known as " wound 

 response." It was found that if a definite 

 region of the bark was tapped several 

 times at short intervals the yield of 

 rubber increased considerably at each 

 tapping. Many methods of the coagu- 

 lation of the latex were also tried, result- 

 ing in the preparation of the now familiar 

 thin " biscuits." The net result was to 



