THE FUNGI 269 



again we come to the hymenium itself, which is thus 

 composed of the terminal cells of the same hyphse which 

 constitute the trama and sub-hymenial layer (Fig. 108). 

 In this last part of their course the filaments have 

 diverged from their original direction to such an extent 

 that they now stand at right angles to the surface of 

 the lamella. 



The hymenium consists of a palisade-like layer of 

 club-shaped cells rich in protoplasm. Some of these are 

 more slender than the rest, and remain sterile, bearing 

 the name of parapliyses. The others are of stouter build, 

 and are the spore-producing elements, here called lasidia. 

 Each basidium gives rise at its free end to from two to 

 four minute peg-like outgrowths (the sterigmata), each of 

 which enlarges at the tip to form a basidiospore (see Fig. 

 108, C, s). The spores when ripe contain oil, and have 

 each two nuclei. These are derived from the basidium, 

 which at an earlier stage possesses a single nucleus 

 formed by the fusion of two or more nuclei which it 

 originally contained. The nucleus of the basidium 

 divides repeatedly, and the daughter-nuclei pass over into 

 the basidiospores, two into each. 



This mode of fructification, consisting of basidia bear- 

 ing spores on sterigmata, is universal throughout the 

 great order to which Agaricus belongs, hence called the 

 Basidiomycetes. The subdivision of this order, represented 

 by Agaricus, is characterised by the hymenium being ex- 

 posed to the air when ripe, and bears the family name of 

 the Hymenomycetes. The basidium, when it has once 

 produced its two or four spores, is exhausted, and does 

 nothing more ; but for a time new basidia may arise, 

 growing up between the old ones. 



An immense number of spores are produced from the 



