140 HEART-ROT CAUSED BY OTHER FUNGI 



by the mycelium. 1 have found similar conidia in larch 

 wood, rotted by P. Schweinitzii, which has been allowed to 

 lie about in the laboratory for some years, but have so far 

 been unable to induce the conidia to germinate. I hope in the 

 future to carry out further experiments with them to ascertain 

 their relationship with the fungus that rotted the wood. 



Trametes Pini, (Thore) Fr. This is another wound parasite 

 of the conifers which rots the heart-wood, and, to a limited 

 extent, the sap-wood as well. According to Hartig it only 

 gains admission to the tree through wounds caused by the 

 fall of live branches. Unlike Polyporus sidphureus, it is by 

 no means confined to trees growing in the open, but has 

 proved destructive in plantations of forty years old and 

 upwards. In woods of this age, owing to thinning, more 

 space is given for the development of the crowns of individual 

 trees, and consequently the branches reach a greater size. 

 They are then more liable to be broken by wind or snow, 

 especially on the more exposed edges of plantations, and it 

 is in such exposed positions that the fungus is most pre- 

 valent. Hartig (1878) has noted that the frequency of 

 the disease on its four European hosts, Scots pine, larch, 

 spruce, and silver fir, is in the order given, being greatest 

 in the Scots pine and least on the silver fir, and that the 

 frequency of broken branches follows the same order. 

 Wounds left by the breaking off of small branches do not 

 admit the fungus, as they are almost immediately pro- 

 tected by a layer of turpentine and resin. But when a large 

 branch breaks the broader core of heart-wood, which does 

 not secrete these substances, is not so easily protected, and 

 it is in the central portion of such a wound that the fungus 

 first begins to grow. Thus inception of the disease generally 

 occurs at some height above the ground. 



The disease affects the same genera of conifers in America 

 as in Europe, with the addition of Tsuga, the hemlock 

 spruce. It has also been reported as growing on willow 

 (Stevens, 1913). In Britain, at any rate in the south of 

 England, it is fortunately uncommon, so that it cannot be 

 included as one of the more dangerous pests of larch cultiva- 



