400 Groom .—‘ Brown Oak * and its Origin. 
the phloroglucin test to the presence of one of the number of substances 
capable of causing the carmine coloration. 
3. The substance is singly refractive. 
As the chemical nature of such wood-gum (in wound-wood, true heart- 
wood, and false heart-wood) is unknown, and as it is not wood and there is 
no evidence that it is gum, in the sequel the substance in question will be 
termed ‘ the brown substance ’. 
Tannin is present in the brown bodies under discussion. To its 
presence they owe their blue-black coloration in ferrous sulphate, and deep 
staining in methylene blue, lactic blue; also their deepened and lightened 
tint in caustic potash and hydrochloric acid respectively. But tannin is not 
an essential part of the substance in question, as parts of one and the same 
brown body are respectively devoid and possessed of tannin. 
As the term ‘ tannin ’ is here used merely to indicate a substance that 
responds to the test for certain tannin-bodies by assuming (in this case) 
a blue or blue-black colour with ferrous sulphate, it follows that the tannin 
present in the brown heart-wood is either different from that of normal 
heart, or if identical is in larger quantity, or is held more firmly by the 
walls (and brown substance). The second possibility is excluded by the 
analysis given later in this paper. 
Biology and Effects of the Fungus. 
For the sake of clearness, the succeeding description refers to wood 
that had been subjected to the treatment (boiling, hydrofluoric acid, and so 
forth) which has been described, and which had removed the tannin more 
or less completely from cells not changing nor changed into ‘ brown oak \ 
(a) Heart-wood of normal colour. 
Immediately within the normal heart-wood (devoid of hyphae) was 
a region of the same colour and for the most part free from hyphae, yet 
here and there showing some of these in vessels and wood-parenchyma. 
These hyphae were often dotted with glistening globules, but no masses of 
‘brown substance ’ occurred. Nearer to the more central ‘brown oak’ the 
main mass of the wood was devoid of hyphae and brown substance, though 
both of these showed (in tangential sections) sporadic patches of cells in the 
medullary rays containing hyphae and the ‘ brown substance which was 
yellow. 
Still nearer to the ‘ brown oak ’ the heart-wood, either normal or more 
yellow in colour, showed hyphae and brown substance arranged in longi¬ 
tudinal strands, and in some medullary rays, while the remaining tissue was 
normal in contents. This distribution of hyphae and brown substance in 
longitudinal strands thus is preparatory to the later stage already described, 
in which the wood is traversed by brown stripes. Both are due to the fact 
