HYMENOMYCETES. ' 97 



character by which the nearly allied members of this 

 class of plants can be distinguished. 



The fructification of the Fungi occurs in two dis- 

 tinct forms, in one of which the seeds or spores are 

 naked, and situated at the ends of slender cells or 

 filaments, whilst in the other the spores are contained 

 in usually flask-like cells, called asci, similar to those 

 occurring in the Lichens. In a few Fungi, antheridial 

 organs, called spermogonia, as in the case of the 

 Lichens, have also been detected. The Fungi are 

 divided into six Orders, from each of which a few 

 species may be selected to illustrate their structure 

 more in detail. 



HYMENOMYCE'TES (v^v, membrane, ILVKVIS, fungus). 

 This is the highest Order of Fungi, containing a large 

 number of genera and species ; as examples of which 

 may be mentioned the common Mushroom, Toad- 

 stools, &c. 



Their general structure may be illustrated by the 

 examination of the common Mushroom (Agai^icus 

 campes'tris) ; the species figured (PL VII. fig. 1), how- 

 ever, being Agaricus micdceus, which is common at 

 the root of trees, the bottom of decaying posts, &c. 



The vegetative part of the fungus consists of a 

 cotton-like mycelium, which is composed of slender, 

 colourless, interwoven filaments, popularly known as 

 the spawn. The portion commonly called the mush- 

 room corresponds to the fructification, and consists 

 of certain parts visible to the naked eye. These are 

 an expanded portion at the top, forming a hemi- 

 spherical cap, receptacle, or pileus (pileus, a cap), and 

 a stalk, or stipes, upon which the cap is supported. 

 On the under surface of the cap are a number of 

 nearly parallel, radiating, dark-coloured plates or gills, 

 somewhat resembling the gill-plates of a fish. The 

 dark colour of the gills arises from the presence of 

 the spores, which are coloured, although in some 

 species they are white. The surface of the gills, upon 



K 



