136 FLOWERLESS PLANTS 



of the fungi belonging to the sub-order Pyreno- 

 mycetes are the truffles. Many species of these 

 strange underground plants are verj' rare, and 

 those which might be called common are not 

 to be found save in hmestone districts. 



In a broad way it is possible to divide all 

 classes of fungi into two sections : those which 

 live on organic matter that is dead, such as 

 rotten leaves and wood or decajdng animal 

 matter, and those which are actual parasites 

 on living plants or animals. The former class 

 of fungi do no harm, and may even do a cer- 

 tain amount of good in aidmg the processes of 

 decomposition. It is an altogether different 

 matter when we come to the parasitic fungi, 

 many of which do more harm than anj^ other 

 pests that it would be possible to name. Of the 

 larger kinds of harmful fungi, those which are 

 parasitic on forest trees are the most conspicu- 

 ous. In this country, where forestry is a sadly 

 neglected industry, people scarcely realise with 

 what the woodmen in some parts of the world 

 have to contend. A fungus which is very 

 common in many parts of Europe, including 

 the British Islands, is a most destructive para- 

 site. The plant is kno\\Ti as Fames annosus, 



