H 



Bulletin 138. 



longer ones are shorter ones which reach, some only a little distance 

 from the margin of the pileus, while others reach half or two-thirds 

 the way to the stem. The space is thus used to good purpose, 

 and the entire under surface of the pileus is crowded with these gills 

 or lamellae. 



The shape of the gills as well as their position can be well seen in 

 figure 97, which is a photograph of a longitudinal section of a mature 



plant. On the 

 right is rep- 

 resented an 

 entire or long 

 gill, which re- 

 minds one 

 somewhat of 

 the blade of 

 a knife. On 

 the left are 

 represented 

 two of the 

 short gills 

 which lie in 

 front of one 

 of the long 

 ones. The 

 surface of 

 these gills 

 forms what is 

 termed the 

 fruiting sur- 

 face of the 

 mushroom, or 

 hy menium. 

 The structure of the gill is quite specialized, and here we find parts 

 which are characteristic of the great group of plants to which the 

 mushroom belongs. If we cut very thin slices or sections across a 

 few of the gills, and mount them in water under a thin cover glass 

 for examination with the microscope, we shall see revealed these 

 peculiarities. Figure 98 represents such a section of two gills. We 



96. — Agancus campest?'is. Vi("iu of under side of pileus^ 

 showing arrangement of gills. 



