224 DISEASES OF TREES 



appears in a structure. In the book which I have quoted I have 

 thoroughly discussed all these matters. 



Amongst the saprophytic wood-fungi, Peziza ceruginosa 

 excites a general interest. Although belonging to the Dis- 

 comycetes, it may be mentioned in this place, as it is to it 

 that the so-called " green-rot" of wood is due. When much- 

 decayed wood, of the oak and beech especially, less frequently 

 of the spruce and birch, lies constantly soaked on the ground 

 of the forest for a long time, it frequently assumes an intense 

 verdigris-green colour. This is due to the wood being occupied 

 by the mycelium of the above-named fungus, which, along with 

 the saucer-shaped sporophore, is vividly green in colour. The 

 green pigment, which may be extracted, is also present in the 

 walls of the elements of the wood. 



On account of its indestructibility the green colouring matter 

 finds employment in the arts, and recently experiments have 

 been instituted to produce green-rot in wood on a large scale by 

 artificial propagation. 



The so-called "blueness" of coniferous wood is due to a 

 Pyrenomycete, Ceratostoma piliferum (Sphceria dryina), whose 

 brown mycelium enters the stem by the medullary rays, and very 

 rapidly reaches the pith. It is specially common in pine woods 

 on unhealthy trees, such as those which have suffered from 

 caterpillars, or it may appear in a heap of damp fagots. 

 Probably on account of deficiency of moisture it rather avoids 

 the duramen, whereas the alburnum is often quickly occupied by 

 the mycelium, and destroyed. 



