THE DESTRUCTION OF WOOD BY FUNGI 371 



Horse Chestnut, Pear, Mountain Ash, Oak, Elm, Ash, Willow, 

 Birch, Lime, Walnut, and Hazel. 



The fruit-bodies of Poly poms squamosus are the largest 

 among British fungi. Few other species growing on trees form 

 such conspicuous objects. During the summer of 1905 the 

 writer gathered a perfect specimen 2 ft. 2 in. across, and having 

 a perimeter of 6 ft. 3 in. It weighed approximately 6\ lb. As a 

 rule, however, the fruit-bodies are not so large. Usually they 

 occur several together, and the largest are then about a foot 

 in diameter. 



The fruit-bodies are annual. They are produced from May 

 till September. In the Midlands of England they are especially 

 abundant in July. If developing in warm, sunny weather, 

 insects soon find them out, causing them to become infested 



AM R B 



Fig. 2. 



Mag. k. Section through a fruit-body of Polyporns squamostis showing the hymenial tubes 

 from which clouds of spores are falling. 



with larvae often before reaching maturity. They may thus 

 become putrescent and fall within a few days or weeks after 

 being formed. This is particularly the case with large speci- 

 mens. A fruit-body is nothing more than an organ of repro- 

 duction. Its function is to produce, liberate, and entrust to the 

 winds millions of microscopic spores. On the under side of a 

 fruit-body of P. squamosus are developed some thousands of 

 narrow hymenial tubes, which have their axes vertically placed 

 and their mouths or pores freely opening below (Fig. 2). The 

 spores are produced by the hymenium with which the tubes 

 are lined. It was found that the spores are discharged with 

 violence from their sterigmata. They are shot out horizontally 

 to a distance of about o*i mm. They then make a sharp turn 

 and fall vertically downwards in the tubes, without danger of 



