HEART-ROT CAUSED BY OTHER FUNGI 137 



alder, willow, poplar, walnut, pear, and larch (Hartig, 

 1894) ; in America it is recorded on a similar range of 

 broad-leaved trees, but appears to be much more general 

 on conifers, and is reported as a parasite on pine, spruce, 

 hemlock spruce, &c. (Schrenk, 1900 ; Atkinson, 1901). It is 

 not uncommon in England, where it is most frequent on 

 the oak, but also attacks the larch, yew, and other trees. 

 Infection generally takes place through wounds left by the 

 pruning or breaking of large branches, so that single trees 

 grown in the open are much more liable to attack than 

 plantations in which side branches are killed before they 

 attain sufficiently large size. Branches which die naturally 

 through being shaded by the crown are less likely to intro- 

 duce the fungus, but Atkinson observed one case in the 

 American white oak in which the fungus had apparently 

 entered through a dead leader which had become included 

 in the gradually thickening trunk. This, however, is excep- 

 tional, and the occurrence of the disease in larch woods 

 may be regarded as evidence of an open canopy which has 

 allowed undue development of side branches. In parks, 

 where such development is normal, the snow-break, or 

 wind-break, of large branches will furnish ' infection courts ' 

 for the fungus, unless the timely treatment of such wounds 

 is resorted to. 



The fungus makes large annual bracket-shaped fructifica- 

 tions which are usually imbricated, i. e. a number grow 

 together, one above another, and are generally found on 

 wound surfaces between May and September. They are 

 easily recognized from all. other polypores by their colour, 

 being bright orange above and sulphur yellow below. The 

 soft flesh of young fructifications is full of a clear yellow 

 fluid, and the upper surface particularly is very moist and 

 turns brown when bruised. This surface is somewhat hairy 

 and when mature becomes hard and brittle. Drops of water 

 containing melezitose (Schrenk) collect on the lower side, 

 which is marked by very fine pores. The whole fructifica- 

 tion develops very quickly, and soon after maturity is 

 destroyed by grubs. 



