(JKNKKAL IXTUODrcTION 



which on breaking away may form an armulus in some of these 

 For details see the introduction to these genera. The essential 

 parts are the gills and pileus and these are presenl in everj species 

 described in this book; the stem, however, is also usually presenl 

 and such a fruit-body -is a typical Agaric. The tissue of the fruit- 

 body is primarily an aggregation of hyphae, and hence merely an 

 extension of the mycelium, compacted to form a specialized Btruc 

 hire. When a portion of the pileus is cut radially, or of the stem 

 longitudinally, and magnified with the microscope, it is seen thai 



these are merely masses of parallel or interw n\ en hyphae COmpo 



ol cells, very similar to tli"-.' of the mycelium. Some of it is special- 

 ized to be sure, as is the cuticle of the pileus or stem; sometimes 

 portions are gelatinous, ethers hardened or encrusted, bul this is 

 mere evident in the mature plant. The tiny beginnings of the mush- 

 room are composed of much the same kind of hyphae throughout. 



The Pilous- 



The pileus is essential in that it bears the ^ills. There are only 

 a lew known species in which the gills radiate out from the top 

 of the stem minus any cap. ami these constitute the rare genus 

 Montagnites, none of which are known in our state. The principal 

 parts el' tin 1 pileus are the surface layer, the margin, ami the flesh 

 or trama. For the many variations of the structure ami form of 

 these ii is accessary to consult the glossary, i See also Fig. 1.) The 

 trama may however, be briefly considered: in the young, fresh or 

 actively developing fruit-body the hyphae of the trama are usually 

 compact ami appear like actual filaments, hut as it approaches 

 maturity the hyphae varies. In some e. g., Coprini, the cells of the 



hyphae quickly loosen from each other and become rounded, and the 



whole pileus. if not quickly dried by the wind, collapses. Others 



are le.ss evanescent and in these the tramal hyphae. although 



loosened considerably, support the pileus for some days. Many of 

 the larger forms, e. g., Tricholomas, retain their compact form for a 



long time, and in tough species like Lentinus the hyphae of the 



trama appear to retain their close-lying position unchanged. The 



trama of the Laetariae is unique and is described under that group. 



Many of the smaller Agarics like Mycenas and Galeras have 

 comparatively few layers of hyphae. often of very large cells. 



