88 HEART-ROT 
across a number of annual rings and even reach the cambium 
when the attack is more marked on one side. This may 
specially be seen in a rootstock when the fungus has entered 
the tree through a lateral root. 
Owing to this red colour the earlier stages of the disease 
are sometimes known by foresters under the name of ‘ red 
rot’. 
The red colour is ascribed by Hartig to infiltration of 
the wood by turpentine and resin, which are secreted by the 
resin ducts and medullary rays. If shavings of the red 
wood are soaked for a considerable time in methylated 
spirit, the turpentine and resin are dissolved and the colour 
disappears, except in the medullary rays which retain 
a reddish-brown tinge. Osmic acid stains part of the con- 
tents of these medullary rays a deep black, and it is probably 
the proteins which both give this reaction and cause the 
red-brown colour in these cells. In the specimens that 
I have examined the medullary ray cells have been all dead 
and no nuclei could be traced. Stray hyphae were often 
found in the red rot region, and where hyphae could not be 
seen the occurrence of the empty bore-holes proved that they 
had formerly been present. Hyphae were even seen in the 
normal coloured wood outside the turpentine region. 
(ii) Soluble gum. During the red rot and earlier stages of 
attack a large amount of soluble gum is present in the 
tracheides and medullary rays. It can easily be seen in 
microscopic sections mounted in alcohol, in which it takes 
the form of an emulsion in the tissues. On addition of 
water this vanishes. It may be extracted by soaking in 
water shavings of wood, which has reached the red rot 
stage. When the water is poured off and filtered, it is 
found to be slightly opalescent, and on adding an excess of 
alcohol the gum is thrown down as a flocculent precipitate. 
This may be collected by filtering, and on drying the filter- 
papers it remains as a yellowish mass. This is readily 
soluble in water, so that a strong and moderately pure 
solution may be obtained in this way. From 600 grm. of 
red rot shavings I obtained 22 grm. of gum. When dry it 
