3*4 



GENERAL MORPHOLOGY OF PLANTS 



ring or annulus (fig. 282). In fig. 283 is a section of the gills 



showing the club-shaped basidia with the sterigmata bearing 



the spores. In the cultivated forms there are often only two 



spores to a basidium, while in the field form there are usually 



four. 



476. Development of the mushroom. The development of 



the mushroom is briefly as follows: The mycelium spreads through 

 the soil or substratum, forming fine white 

 cords. This is known as the spawn. 

 When this is well established small rounded 

 compact masses of mycelium are formed 

 on the cords. These are the young 

 fruit bodies which are to develop into the 

 mushroom. When they become from 3 mm. 

 to 5 mm. in diameter, the parts of the 

 mushroom are differentiated, the upper 

 part into the cap, the lower part into the 

 stem, and the outer portion midway forms 

 the veil. Inside of this veil the hymenium 

 begins to form on the underside of the cap, 



and a circular opening is formed by the parting of the tissue 



between the veil, the 



upper part of the 



stem and the cap. 



This leaves room for 



the development of 



the gills which grow 



downward from the 



cap. This is the 



" button" stage of 



the mushroom. All 



parts continue to 



expand, the stem 



elongates, the cap 



broadens, and the 



veil becomes well formed. 



Fig. 284. 

 Portion of hymenium 



Fig. 285. 



Cluster of young mushrooms, a few of the larger ones 

 developing to maturity. 



Finally the veil ceases to grow. 



