March i6, 1922] 



NA TURE 



357 



clean locally. They are living structures, and 



jir power of resistance varies with the general 



ilth, and this, like the health of the teeth, mainly 



jends on a supply of natural foods in proper 



mtity, especially in early life when tooth-formation 



;urs. Early life means especially embryonic life, 



the proper feeding of expectant mothers is a 



qua non. Sophisticated and patent foods are 



Bcially harmful, for they, as a rule, lack the neces- 



r\- " vitamins," which were then described in out- 



le. Bad teeth in their turn undermine the general 



ilth, and, by forming foci of infection, lead to 



leral ill-health, indigestion, blood-poisoning, rheu- 



itoid affections, and the Uke, and so a vicious 



le is produced, the abolition of which becomes a 



Itional duty. 



After a general account of what is called " calcium 

 metabolism," a series of lantern-slides was shown 

 to illustrate not only the structure of the various 

 parts of a tooth, but also the stages in their develop- 

 ment, in which the cells responsible for the elabora- 

 tion of the enamel prisms and the layers of dentine 

 with its tubules and the nerves, etc., within them 

 were seen. Occasion was taken to press home again 

 the possibilities of injury and the necessity for care, 

 especially in early stages and in early Ufe. the word 

 " early " including foetal life. In conclusion, the 

 lecturer looked forward to a time in the not far 

 distant future when the teeth of the nation might 

 be its pride, and not a source of lamentation and 

 pain. 



The Brown Bast Disease of the Para Rubber-tree. ^ 



By Dr. S. E. 

 kURING the early years of rubber planting in the 

 East considerable optimism prevailed in certain 

 quarters as to the powers of the Para rubber-tree 

 (Hevea hrasiliensis) to resist disease in its new home. 

 The planting of such great areas with a single crop 

 plant, however, was practically certain to result 

 sooner or later in fungal disease, to say nothing of 

 insect attack ; and, although little was (and still is) 

 known as to the functions of latex in plants, it was 

 safe to predict that the regular withdrawal of con- 

 siderable quantities of latex from the trees would 

 result in physiological disturbances which might 

 become a factor of commercial importance. Events 

 have proved these views to be well founded. As com- 

 pared with many crops, rubber has been comparatively 

 free from visitations, but several fungal diseases are 

 now recognised and insect pests are not unknown ; 

 while a disease hitherto ascribed to physiological 

 causes, and known as " brown bast," has attained 

 such importance as to constitute the most dangerous 

 cultural menace to the rubber-planting industry at 

 the present day. 



Brown bast is a disease of the bark * of tapped 

 trees, but it does not involve the death of the tree, 

 or even of the affected bark. The disease may be 

 recognised by a difficulty in obtaining latex on tapping 

 to the usual depth, followed ultimately by the cessa- 

 tion of latex flow (when the tree is said to be " dry "), 

 and is further characterised by a brownish or olive- 

 green discoloration of the middle and inner bark, 

 which may show a definite brown line on the tapping 

 cut near the cambium. External signs of the disease 

 may be lacking, but in the more severe cases the 

 iter bark often scales and splits longitudinally and 

 1 exudation of latex occurs. This condition some- 

 ames results from the secondary development of 

 woody " burrs," nodules, or plates within the diseased 



' (i) " Brown Bast Disease of Plantation Rubber, its Cause and Pre- 

 ution." By R. D. Rands. Mededeelingen van het Instituut voor 

 iiitenziekten, Departement van Landbouw, Nijverheid en Handel, No. 



(1921) ; overgedmkt uit her Archief voor de Rubbercultuur, Jaargang V., 



. 5 (Mei 1921). 



z) " Histological Studies on the Brown Bast Disease of Plantation 



l>ber." By R. D. Rands. Mededeelingen van het Instituut voor 

 .uitenziekten, Departement van Landbouw, Nijverheid en Handel, No. 49 



(3) "Brown Bast: An Investigation into its Causes and Methods of 

 Treatment." By A. R. Sanderson and H. Sutcliffe. Pp. 71 + 26 plates. 

 'London : The Rubber Growers' Association, Inc., n.d.) 7s. 6d. net. 



1) " Over den Steencellenjing in de Schors van Hevea." Door Johannes 



:idrup. Mededeelingen van het Besoekisch F*roefstation, Rubberserie, 

 19 (1921) ; overgedmkt uit het Archief voor de Rubbercultuur, Jaargang 

 .. .\o. 9 (September, 1921). 



s) "On Brown Bast and its Immediate Cause." By J. B. Farmer and 



S. Home. India-Rubber Jotirtuil, vol. 61, No. 25, June 18, 1921. 



■>) " Phloem Necrosis (Brown Bast Disease) in Hevea brasiliensis." By 

 ..:;hur S. Home. Annals of Bolany, vol. 35, No. 139, July 1921. 



' The term " bark " is here used in the planter's sense of the tissue 

 actually involved in the tapping operation. 



Chandler. 



tissue, and, unless the case is dealt with, these bodies 

 may cause the bark ultimately to become so knotted 

 and irregular as to be useless for tapping purposes. 

 The formation of burrs and nodules, however, is not 

 necessarily associated with brown bast, as has been 

 shown by Bateson, Bryce, and others. 



Brown bast was widely reported as an epidemic in 

 the plantations during 1916-18, and a satisfactory 

 method of treatment became a matter of prime im- 

 portance. Pending exact knowledge as to the cause 

 of the disease, the methods recommended were based 

 on the observations that affected latex-vessels do not 

 again function, that the diseased portion of the bark 

 is useless for further tapping, and that the disease 

 " spreads " in the bark. Planters were therefore 

 advised to remove the diseased tissue, either by 

 " scraping " the brown bast tissue from the bark, or 

 by carefully " stripping " off the bark down to the 

 cambium. In the latter case, especially, measures 

 should be taken to protect the delicate exposed sur- 

 face so that a satisfactory regeneration of the bark 

 by the cambium may take place. The removal of the 

 superficial layers of the affected bark, followed by the 

 application of warm tar to the exposed surface, has 

 also been practised. 



It was early recognised, however, that the best 

 chance of devising adequate measures of control would 

 result from a correct understanding of the nature of 

 the disease, and considerable research on this subject 

 has been carried out by British and Dutch botanists 

 in the East. So far, attempts to associate the disease 

 definitely with bacterial or fungal attack have failed, 

 and at the present time brown bast cannot be ascribed 

 to any causal organism, though it has been claimed 

 by Keuchenius that bacteria are present in the 

 diseased tissue. With the bulk of evidence against a 

 parasitic origin, of the disease, most investigators have 

 fallen back on the theory that brown bast is a physio- 

 logical disease, the result of metabolic disturbances 

 as to the nature of which, however, little or no in- 

 formation is available. 



Recently a series of important publications on 

 the etiology of brown bast have appeared almost 

 simultaneously. The results obtained are of ex- 

 ceptional interest, inasmuch as the work has been 

 carried out by investigators widely separated and work- 

 ing independently on material derived from several 

 different planting countries. Rands (i) and (2) 

 has dealt with the disease in Java and Sumatra ; 

 Sanderson and Sutcliffe (3) in British Malaya ; 

 Gandrup (4) in Java ; while Farmer and Home (5) 

 and (6), in London, have examined diseased material 

 from British North Borneo and Malaya. These in- 



NO. 2733, VOL. 109] 



