290 Studies in Forestry [CHAP. xiu. 



years ; if possible a different species of plant should be pricked 

 out from what has previously been sown there. Watering 

 the seed-beds with a solution of 4! Ib. of copper vitriol (blue- 

 stone) and one quart of ammonia in fifty gallons of water is 

 said to yield good results in checking the spread of the 

 disease. 



Minor disorders are occasioned by Rhytisma acerinum which 

 causes the yellow spots (Xyloma acerinum, the summer form), 

 that change in autumn and winter to black, on Maple and 

 Sycamore foliage, Melampsora tremulae on Aspen, and M. 

 Hartigii on the leaves on the one-year-old shoots on Willows : 

 this last disorder is often serious on S. acutifolia and S. caspica. 

 A similar fungus, M. salidna, is also found on Willows, on S. 

 caprea chiefly, and M. Betulina on the Birch. In all these cases 

 the burning of infected foliage should be seen to during autumn 

 and winter; whilst in osier-hags infected shoots should be cut 

 away and burned wherever the disease manifests itself. 



II. FUNGOID DISEASES OF THE STEM OR BRANCHES 

 (in the bark or in the wood). 



A. On Conifers : 



i. Trametes pini, Fr., the Pine Fungus. 



This disease is to be found chiefly in Pine stems from about 

 forty years of age onwards, although it also occurs on Larch, 

 Spruce, and Silver Fir. The spore-tubes insinuate themselves 

 into the woody tissues on wound -surfaces or wherever green 

 branches have been broken off. When the germination of the 

 spores begins, the hyphae push forward, destroying the cell-walls 

 and forcing their way into the heart-wood of the tree. Here the 

 mycelium develops, and forms ring-shakes or heart-shakes 

 extending down from the crown and leading to the rapid 

 decomposition of the timber in consequence of the rapid 

 increase of the mycelial filaments, whilst as a rule the sapwood 

 remains untouched. The mycelium next makes its appearance 



