290 



The Supplement to the Tropical Agriculturist 



known to the Thos people as "Teo-non." At the 

 time it was not possible to define the systematic 

 position of the plant beyond its affinity with 

 Ulmaceae. Since then, however, it has been re- 

 cognised as a member of the genus Bleekrodea 

 (Moraceae) and has been described as B. tonkinen- 

 6'is by Dubard and Eberhardt in C ompt. Rend. Ac. 

 d. Sc. Paris, vol. OXIV., Oct. 1907, p. 631. The 

 examination of a few branchlets of the plant, 

 recently received at Kew from Dr. E, Perrot, 

 has confirmed the conclusions of the authors as 

 to its affinity and specific distinction. The genus 

 Bleekrodea has so far been known only from two 

 species, one a native of Borneo (B. insignia, Bl.) 

 and the other of North- West Madagascar (/?. 

 madagascariensis, Bl.) It has already been de- 

 scribed by Blume as laticiferous,a character very 

 general in Moraceae, but, so far as we know, there 

 is no evidence of the presence of caoutchouc in 

 the latex of the two species recorded by him. On 

 the other hand, B. tonktnensts is stated to be very 

 rich in caoutchouc and in this respect reminds 

 us of another Moraceous genus, Castilloa. 



The occurrence of a rubber-yielding tree in 

 the forests of Tonkin was recorded as early as 

 1905 in a report by the Commanding Officer of the 

 Oercle of lhat-Khe in the province of Bac-Kan. 

 According to him it was known as ' May-teu- 

 nong,' and attained a height of 10 — 12 m. with a 

 diameter of 40 cm. The latex was abundant and 

 was collected by the natives, whose attention 

 seems to have been directed to the tree quite re- 

 cently and accidentally; in fact they used it only 

 as an admixture to increase the bulk of rubber 

 collected from other sources. Last year, how- 

 ever, Dr Eberhardt was commissioned to investi- 

 gate the properties of the tree on the spot and 

 the conditions under which it grows. The follow- 

 ing is the essence of his report. 



The tree occurs practically all over the province 

 of Bac-Kan (north of Banoi,and halfway between 

 this town and the Chinese frontier), and in the 

 adjoining southern parts of the Cercles of Bao- 

 lanc andCao-bang; but Dr Eberhardt is inclined 

 to believe that it will be found throughout the 

 mountainous districts to the north-west of the 

 delta of the Red River and in the Laos country. 

 In the province of Bac-Kan, it prefers hilly 

 ground with a subsoil of calcareous schist and a 

 deep covering of humus, which, however, must 

 be fresh and well aerated and free from stagnant 

 water, where the soil is charged with clay, the 

 ' teo-non' disappears completely, giving way to a 

 vigorous growth of bamboos. It grows gregari- 

 ously and may constitute as much as 40 percent 

 of the vegetation. It is a rapid growing, much 

 branched tree and attains a height of 12 to 15 m. 

 The bark is thin and white, the wood white, 

 soft and useless for joinery and carpentry. The 

 mode of collecting the latex employed by the 

 natives is very crude and wasteful. It consists 

 in tapping the tree near its base by as many cuts 

 as possible so that the normal flow of the latex 

 is soon interrupted, whilst at the same time the 

 tree is rapidly exhausted. Moreover, the pro- 

 duct becomes in this way much contaminated 

 With impurities. The latex is collected in the 

 hollow joints of bamboos and carried to the 

 nearest village or to some water-course where 

 the contents are poured into a pot containing 



water which is then heated to boiling point. 

 Thus treated it forms into cakes, the impurities 

 nearly always gathering in the centre. There 

 are two seasons for collecting the latex, one be- 

 fore, and the other towards the end of the rainy 

 season. The natives, however, generally confine 

 their efforts to the latter time, when the flow is 

 much more abundant. This is due to the in- 

 creased activity of the organism and to the pre- 

 sence of a greater quantity of water in the latex, 

 so that finally the amount of caoutchouc 

 obtained is after all not greater at the 

 end than just before the beginning of the 

 wet season. Similarly the trees on the outskirts 

 of a 1 teo-non ' wood yield less but more concen- 

 trated latex. At the end of May Dr. Eberhardt 

 obtained from a single tree of 20 cm. in diameter 

 as much as 480 grammes of latex; but he thinks 

 that in the autumn this tree might well have 

 yielded 600-650 grammes. He recommends tap- 

 ping at the base of the trees as the latex taken 

 from the young parts does not coagulate. In 

 this respect the ' teo-non' behaves like Ficus 

 and Castilloa. 



Dr. Eberhardt obtained 676 - 6 grammes of 

 caoutchouc per kilogramme (or 67 '6 per cent) 

 from two litres of latex. The best method of 

 inducing coagulation was by means of sulphuric 

 and hydrochloric acids; acetic acid seems to 

 impair the natural cohesiveness of the caout- 

 chouc globules. Heating directly over 

 tire results in an inferior product ; as it has 

 to be continued until the serum is completely 

 evaporated when a succession cf thin and tough 

 skins is formed which do not adhere to each 

 other. On the other hand, the hot water bath 

 gives excellent results. The treatment with 

 sulphuric acid, however, seems to be by far the 

 best process and the caoutchouc thus obtained 

 is of first-rate quality, very strong (nerveux), 

 resistant and elastic. Mr Oibot, an expert in Am- 

 erican rubber and in the rubber industry gener- 

 ally, states that the ' teo-non ' rubber is equiva- 

 lent to Para and practically indistinguishable 

 from it. A native-made cake of ' teo-non ' rubber 

 was, in fact, awarded a gold medal at the F rench 

 Colonial Exhibition at Marseilles in 1906, in spite 

 of the usual impurities present in the native 

 article. 



A score of young plants are at present in culti- 

 vation in the Botanic Garden at Hanoi. Only 

 one member of the small sub-tribe Fatoneae, to 

 which Beekrodca belongs, has been found up to 

 the present in India, viz. : PscudostreMus indica, 

 Bur,, a small tree of the Khasia Hills ; but be- 

 tween them and Tonkin, there must be many 

 localities where ' teo-non ' could be grown with 

 success if it should be found that its natural area 

 does not extend into British territory. 



Of three branchlets received from Dr Perrot, 

 two possess only male clusters, the third only fe- 

 male cymes with or without rudiments of male 

 flowers. Dr Eberhardt, on the other hand, says 

 that the male and female inflorescences alter- 

 nate, whilst his and Dubard's description in the 

 Comptcs Rendus, I.e., admit male and mixed 

 clusters on the same branch, — Kew Bulletin, 

 No. 6, 1908. 



