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A TEXTBOOK OF THEORETICAL BOTANY 



which during the first year are stimulated by the union, and this is marked 

 by a darker and more vigorous zone of grass plants ; subsequently in the 

 second year, as the Fungus gains the upper hand, the roots are killed and 

 the grass dies. Later, in the third year, after the fungal mycelium has 

 migrated farther out, the grass recovers and regains its normal colour, 

 growing more vigorously on the humus left behind by the dead zone of 

 grass. In the autumn, or in some species, in the spring, the fruiting bodies 

 of the Fungus are developed near the extremities of the mycelium's growth. 



Fig. 312. — Marosmius oreades. Fairy Ring in grass. 

 (From a photograph by H. Bastin.) 



We may therefore regard the ring of fruiting bodies so produced as an 

 indication of the size of the Fairy Ring, and it will be found that this 

 coincides approximately with the well-marked darker grass ring which we 

 can see (Fig. 312). 



As our example of this group we shall consider the Common Mushroom, 

 formerly known under the name of Agariais campestris, but more correctly 

 Psalliota campestris. 



Psalliota campestris (The Common Mushroom) 



The Mushroom grows chiefly in meadows, where its mycelium feeds 

 either on the roots of grasses or on manure and humus deposited in the 

 soil (Fig. 313). 



The mycelium consists of masses of hyphae, frequently twisted together 

 into thick cords or rhizomorphs, which in their early stage are made up 

 of uninucleated cells. Later, two hyphae come into contact and fuse, and 

 a nucleus from one hypha passes into the nearest cell of the other hypha. 



