102 PRACTICAL BOTANY. 



seen, which may also be recognised in the septa in 

 longitudinal sections, as a slight aggregation about the 

 centre of the septum. 



VII. Passing to the pileus of the mature mushroom, 

 cut tangential vertical sections through it in such a way 

 as to traverse the vertical gills at right angles to their 

 surface : great care must be taken that the surfaces of 

 the gills shall not be injured in the process of prepara- 

 tion, otherwise the basidia and spores which project 

 from their surfaces cannot be observed. Mount in 

 glycerine and examine under a low power : the chief 

 bulk of the section will consist of the massive tissues 

 of the pileus, which show little or no differentiation ; 

 passing downwards to the lower surface where the gills 

 or lamellae have been traversed, the sections of these 

 will be seen as fringe-like projections from the lower 

 surface : occasionally branching of the gill may be 

 recognised. 



Examine the sections in detail under a high power : 

 the following observations are to be made 



1. The mass of tissue of the pileus consists of a 

 complicated plexus of much-branched hypha3, with 

 large intervening spaces : it is composed of short cells, 

 similar in their characteristics to those which compose 

 the stipe : the chief difference lies in their arrangement. 

 This spongy tissue becomes denser about the insertion 

 of the lamella. 



2. The sections through the lamellaB show a differ- 

 entiation into 



a. The central portion (trama), in which the sep- 

 tate hyphal filaments are easily recognised running 

 longitudinally down the middle of each lamella, and 



