HEART-ROT 89 
is hard, but readily becomes soft on the addition of water, 
though the solution is not adhesive. 
The gummy nature of this substance, its solubility in 
water and insolubility in alcohol, showed it to be either 
a gum or a dextrin. On hydrolysing for half an hour by 
boiling with dilute H.SO,, it gave large quantities of sugar 
which was capable of reducing Fehling’s solution. This 
led me to suppose that the substance was a dextrin, but 
Dr. D. H. Vernon kindly tested it for me and identified it 
asa gum. The distinction was based on the readiness ‘with 
which an aqueous solution is precipitated by alcohol, and 
on the detection of pentose sugars as a result of its hydro- 
lysis. If alcohol to 51 per cent. be added to a 20 per cent. 
solution of the gum, a dark-brown gummy mass is thrown 
down and a moderate amount of white precipitate is retained 
in solution. If alcohol is added to the filtrate up to 64 per 
cent., a considerable further white precipitate is thrown 
down, while alcohol to 70 per cent. brings down a very 
copious white precipitate. No further precipitate results 
from adding more alcohol, so that we may conclude that 
an excess of alcohol to 70 per cent. precipitates all the gum. 
Dextrins, on the other hand, do not begin to be precipitated 
till the alcohol exceeds 70 per cent. If the solution be 
kept for some time the presence of pentose sugars may be 
detected by the phloroglucol and orsinol tests, which give 
very marked results. And since the gum was derived by 
precipitation by alcohol from a watery extract of the wood, 
it cannot be maintained that the pentose sugars were present 
from the first, as such impurities would not be precipitated 
by the alcohol. 
Now it is known that in the process of delignification 
a number of pentose derivatives are removed from the cell 
walls, and we may here seek the source of the gum found 
in the early stages of rot. Very little is at present known 
about the chemical constitution of gums, and the term is 
applied rather vaguely by biochemists ; but as far as I know 
this is the first occasion in which a member of this class of 
substance has been isolated from a conifer. In the trunks 
