IN CEYLON. 53 



dark reddish brown in colour, which can be extracted from 

 the original ebony dust with alcohol and amounts to 3'58 

 per cent, of the dust. 



The black colouring material therefore contains two gums, 

 one resin, and an insoluble residue composed mainly of 

 carbon. 



It has been asserted that the colouring materials arise by 

 chemical change of the inner layer of the elements in which 

 they occur, and even Molisch believed chat the reputed thinness 

 of the walls of some vessels was due to part of the material 

 having been so modified. My own observations do not 

 confirm this theory, though I have noticed a certain amount 

 of swelling when sections of the fresh wood are placed in 

 water. This is probably due to the absorption of water by 

 the thin layer of gum which forms a lining to the tracheal 

 elements, and which occurs in the yellow or white sapwood 

 of ebony-bearing species. 



From an examination of longitudinal sections of the 

 sapwood and heartwood of our species I have concluded that 

 the greater part, if not the whole, of the coloured materials 

 filling the lumina of the elements is derived from the 

 materials accumulated in the parenchymatous system of the 

 secondary wood. Usually the discolouring substances make 

 their first appearance in the cells of the medullary ray or 

 wood parenchyma, then in the tracheal elements, and lastly 

 in the fibres. 



The parenchymatous elements of the sapwood are invari- 

 ably packed with starch grains, tannin, and calcium oxalate. 

 The starch grains gradually lose their regular outline and a 

 fine granular texture becomes obvious, together with a change 

 in colour. Finally, globules suggestive of a resin or gum 

 appear in the parenchyma cells, and as these increase a deepen- 

 ing of tint from yellow to brown occurs. It would therefore 

 appear that by a series of chemical changes the contents 

 of these elements gradually disintegrate, and the resulting 

 compounds are in the form of globules of coloured material. 

 It must, however, be remembered that starch is a stable 



