44 



TEXT-BOOK OF FUNGI 



In the perennial fungi, as various species of Polyporus, 

 increase in size takes place by the formation of a new 



I'fe 



FIG. 14. Fames fomentarius, a large perennial fungus hav- 

 ing a hard, woody sporophore. The upper surface is sterile, 

 the hymenium being situated on the flattened under surface. 

 A new hymenial layer is formed each season upon the pre- 

 viously existing one. The different layers of hymenial tissue 

 are indicated by lines as shown in the section. Each layer 

 extends a little beyond the previous one, hence the hymenium 

 increases in area each year. The ridges on the surface 

 roughly correspond to the number of hymenial layers. One 

 quarter nat. size. 



hymenial layer on the surface of the preceding one. The 

 hyphae forming this new hymenium also grow round the 



