HEART-ROT 87 
criticism. Certainly the discovery of conidia profoundly 
affected the value of the measures by means of which Hartig 
sought to combat the disease. A more general account of 
the fungus and its effects on trees may be found in the 
translation (1894) by Somerville and Marshall Ward of 
Hartig’s Diseases of Trees. 
Heart-rot is the cause of very serious financial loss to 
foresters. It occurs with alarming frequency in woods 
which are planted as a first rotation on land that has pre- 
viously been arable or waste, and acres of plantations may 
be reduced through it to two-thirds their value or less. 
And since in Britain new land is frequently being converted 
into forest, a conversion which is likely to be much accele- 
rated in the near future, the disease must be regarded as 
one of our most serious enemies. Plantations on old forest 
land, however, remain comparatively free from heart-rot, 
so that we may look forward with more confidence to the 
yield of later rotations on land which is at present being 
afforested. 
Though Fomes annosus is found in North America, it 
does not appear to do so much damage there as other heart- 
rotting fungi. Butler (1903) records its occurrence on 
deodar in India, but his description and figures suggest that, 
if this fungus was present, it was working in collaboration 
with Armillaria mellea. 
In the following sections I shall describe in detail the 
various characteristics of the disease as it appears in the 
larch. Afterwards I shall deal with the methods by which 
the fungus attacks the trees, and with the means of com- 
bating it and minimizing its depredations. 
Seeretions induced by Fomes annosus. (i) Turpentine and 
resin. In the early stages of attack by the heart-rot fungus 
the wood assumes a reddish-brown appearance. This red 
region usually surrounds all parts which are actually rotted 
by the fungus, and advances in front of the heart-rot as it 
ascends the tree. At first it resembles a red duramen, but 
its tone is generally redder and deeper than that of normal 
duramen, and the outside limit of red coloration may cut 
