458 PRACTICAL BOTANY 



centre than at the periphery, and that throughout, inter- 

 cellular spaces are to be recognized. 



Observe under a high power that where the section 

 includes one of the septa (which will thus be seen in 

 surface view), a central highly refractive spot is to be 

 seen, which may also be recognized 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 

 recognized. 



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 lamellae. 



