458 
Notes. 
brown bast in a tree may be suspected when it ceases to yield latex in response to 
tapping, or when the amount of latex obtained at each tapping shows considerable 
diminution, in which case an uneven exodus of the latex can be detected by an 
inspection of the cut surface immediately after the tapping operation has been 
performed. 
Some description of the anatomy of the burrs has been given recently by 
Sanderson and Sutcliffe , 1 who attribute them to meristematic activity of the paren- 
chymatous cells which abut on the diseased laticiferous vessels : the new tissue cells 
may be converted into stone cells or differentiated into woody elements. 
Rands , 2 in a preliminary note, states that the tissues forming the bark of Hevea 
brasiliensis , when wounded, produce a gum which blocks up the intercellular spaces 
and causes a brownish discoloration of the tissue in the neighbourhood of the wound. 
Bobilioff 3 states that as brown bast develops the anatomical changes to be observed 
in the bark include the formation of a brown degenerate substance in the intercellular 
spaces and middle lamellae of the cells. 
Whilst studying transverse sections of the bark taken from certain trees affected 
with brown bast and from trees in which the presence of the malady was suspected, 
using material obtained by Professor J. B. Farmer from British North Borneo, numerous 
minute golden yellow spots of irregular outline were observed in the phloem, in the 
region extending from the neighbourhood of the cambium outwards. With a higher 
magnification the outlines of the coloured granular areas sometimes resembled those 
of intercellular spaces, but were distinguishable from spaces owing to their intersection 
by one or more waved partitions staining more or less distinctly with ruthenium red. 
After a detailed study and careful comparison with the phloem in normal bark, these 
golden areas were found to be the sections of necrotic sieve-tubes which no longer 
showed a reaction for callus with soluble blue ; and the waved outlines in many cases 
could be interpreted as transverse sections of the large vertical sieve-plates which 
form the dominant feature of the phloem of Hevea when viewed in longitudinal 
section. 
In order to be certain that the disease affecting the Borneo material was actually 
brown bast, reference was made to authentic material from the Federated Malay 
States, with the result that similar pathological characteristics were discovered in the 
tissues of the Malayan specimens. 
In the younger phloem the disease is confined to the sieve-tubes, but in the 
middle phloem region the discoloured areas are larger, owing to the fact that other 
cells — phloem parenchyma, medullary ray cells, laticiferous vessels — have become 
involved in the local tissue degeneration. 
Incipient stages in the process of burr formation have been observed. The 
wound cambiums arise in proximity to the diseased laticiferous vessels and often 
completely encircle small groups of vessels. As a result of the activities of the wound 
1 Sanderson, A. R., and Sutcliffe, H. : Brown Bast. Published by the Rubber Growers’ 
Association, May, 1921. 
2 Rands: De bruine binnenbastziekte van Hevea brasiliensis (Voorloopige mededeeling). 
Archief voor de Rubbercultuur in Ned. Indie, 1919, April, Jaarg. iii, p. 156. 
3 Bobilioff, W. : Over de oorzaak der bruine binnenbastziekte van Hevea brasiliensis. Ibid., 
Mai, Jaarg. iii, p. 172. 
