ON THE STRUCTURAL ANATOMY OF FUNGI. 27 



THE HYMENIUM. 



This organ consists of an extremely fine membrane which is 

 spread over certain parts of a mushroom. Upon its surface there 

 are developed innumerable quantities of Spores, perceptible only 

 in the aggregate as impalpable dust. Amoug the larger Fungi 

 the Hymenium is of great superficies, because it is spread over 

 a large number of processes. These processes vary in character 

 in different orders, and -vvill consequently have to be separately 

 studied. The first with which we have to do are the Gills of the 

 order Ajjaricini. 



O' 



GILLS. These are a distinctive characteristic of the order 

 Agai'icini. They consist of thin, lamellar plates, set vertically 

 upon the under side of the Pileus, radiating from the Stem to the 

 Margin. They are really extremely fine prolongations of the 

 substance of the Pileus, coated throughout by the Hymenium. 

 The interior substance of Gills is called the Trama. When the 

 Section has been made we are able to see the flat side of the Gills, 

 and to note their disposition, which is an important feature in the 

 identification of species. The Gills are, for the most part, coloured 

 by the Spores produced upon them, which will be presently ad- 

 verted to. Their conformation, when seen in the Section of a 

 mushroom, is described by terms of which the following are those 

 not yet explained, or generally comprehensible. The end of the 

 Gills nearest the Stem is called Posterior, or Behind ; that nearest 

 the Margin is styled Anterior, or In Front; while the part or edge 

 affixed to the Pileus is looked at inverted and described as Below, 

 or Beneath, the outside or apparent edge being Above. 



Acute, tei'minating in a point at either end. 



Adnate, the postei'ior end squarely set and fixed on the Stem. 



Adnexed, the posterior end fixed to the Stem, but not squarely 

 set. 



Anastomosed, united one to another by irregular junctures. 



Approximate, the posterior end almost adnexed to the Stem. 



Arcuate, arched from posterior to anterior. 



Ascending, from the Margin to the Stem. 



Attenuate, tapered off at either end. 



Branched, dividing from the sides ; also styled Furcate, and 

 Forked. 



Broad, wide or deep vertically, as seen on section. 



