326 



PRACTICAL COURSE IN BOTANY 



375. The hymenium. — Cut a tangential section through 

 one side of the pileus and sketch the section of the gills as 

 4^5.5 they appear under a lens, or a low 



power of the microscope. Notice 

 that the blade consists of a central 

 portion called the trama {Ir, Fig. 462) 

 and a somewhat thickened portion, 

 h, constituting the hymenium, or 

 spore-bearing surface. Now exam- 

 ine, under a high power, a small sec- 

 tion from the edge of a gill, including 

 a bit of the trama. Notice that this 

 last consists of a tissue of mycelial 

 cells (Fig. 463) covered by the hy- 

 menium, or spore-bearing membrane, 

 which is thickly clothed with a layer 

 of elongated, club-shaped cells (6, h 

 and p, p, Fig. 463) set upon it at right 

 angles to the surface. Some of these 

 put out from two to four, or in some 

 species as many as eight, little 

 prongs, each bearing a spore (s, s, Fig. 



Figs. 461-463. — Section of a 

 gilled mushroom : 461, through 

 one side, showing sections of the 

 pendent gills, g, g (slightly mag- 

 nified) ; 462, one of the gills 

 more enlarged, showing the cen- 

 tral tissue of the trama, tr, and 

 the broad border formed by the 

 hymenium, h 463, a small sec- 

 tion of one side of a gill very 

 much enlarged, showing the 

 club-shaped basidia, b, b, stand- 

 ing at right angles to the surface, 

 bearing each two small branches 

 with a spore, s, s, at the end. 

 The sterile paraphyses, p, are 

 seen mixed with the basidia. 



463), while others re- 

 main sterile. The spore- 

 bearing cells are called 

 basidia; the steri e 

 ones, paraphyses; and 

 the whole spore-bearing surface together, the hymenium, from 

 a Greek word meaning a membrane. It is from the presence 



Figs. 464, 465. — A tube fungus (Boletus edidis) : 

 464, entire ; 465, section, showing position of the 

 tubes. 



