444 



BOTANY OF THE LIVING PLANT 



341,343-) The apparently fresh formation of mushrooms from day 

 to day in the fields is thus accounted for. The button-mushrooms 

 are hidden in the grass till the extension takes place. 



t sh , h 



Fig. 344. 



Structure of the hymeniumof the Mushroom Psalliota (Agaricus) campestris. A is 

 a vertical section through the pileus traversing several gills (/). B shows the 

 structure of one gill more highly magnified : hy = the hymenium. C shows a small 

 area of the hymenium in section ( x 350). The basidia project, each bearing two 

 basidiospores, that number being exceptional but regularly present in the Mushroom. 

 (After Sachs.) 



The Mushroom as commonly known is the fruiting-body, borne 

 on the nutritive mycelium. It has the usual toad-stool form, with a 

 stalk or stipe bearing the hemispherical pileus (Fig. 341). As in all 

 large fungal bodies, it consists of false tissue. The hyphae composing 

 it take first a parallel course so as to form the stipe, they then diverge 

 upwards so as to form the wide-spread pileus. In the button stage 

 the margin of the pileus is connected with the stipe by a thin covering 

 of the velum ; but this is ruptured as the mushroom expands, leaving 

 a ring round the stipe (Fig. 341). The radiating gills, which hang verti- 



