128 PROTECTION OF WOODS AGAINST 



unable to form food material for themselves and obtain it from 

 dead or living plants. 



Fungi which obtain their food from dead plants are called 

 saprophytes ; these are not of great importance to the wood- 

 man. Those which live upon living plants are called parasites, 

 and are of the greatest importance in forestry as they cause 

 many bad, and sometimes fatal, diseases among forest trees. 



Fungi are usually formed of many long filaments called 

 hyphae, which together form a mass called the mycelium. 

 This sometimes grows and spreads through living wood or 

 bark, and is often only distinguishable with a microscope. 

 Instead of flowers the reproductive organs are a special 

 collection of cells, the whole being called a fructification, which 

 produces large numbers of minute reproductive bodies called 

 spores, which are, as it were, the seeds of the fungus. In the 

 ordinary mushroom the part above ground, which we eat, is the 

 fructification, the spores being borne on the gills. The mycelium 

 of the fungus is below ground, and is often called the spawn by 

 mushroom growers. The fructifications of most species usually 

 appear for a few weeks only, chiefly about October, but in 

 some species they are permanent, and are then often hard or 

 woody. Warm damp weather is favourable to the spread of 

 the fungi, while strong sunlight is unfavourable to them. 



Some fungi attack sickly trees only, while others damage 

 perfectly healthy ones. It is difficult sometimes to say whether 

 a fungus is the cause of disease, or whether it is the result of 

 previous debility in the tree. 



Fungi are the cause of a great many diseases, especially 

 in coniferous species, and with the larger planting of conifers 

 which is taking place in Great Britain nowadays, disease is 

 likely to spread, and woodmen must be on the look-out so as 

 to take measures early. 



The best general rules for prevention of disease are to grow 

 species only on soils and situations really suitable to them, as 

 they are then stronger and can withstand attack better ; to 



