PSALLIOTA CAMPESTRIS 365 



rings in connection with Psalliota campestris, at least so far as my 

 own experience is concerned, it may be well perhaps to insist that 

 the rings which I observed did as a matter of fact belong to this 

 species and not to Psalliota arvensis. The fruit-bodies were quite 

 typically those of the Common Mushroom, and not those of the 

 Horse Mushroom. Shantz and Piemeisel x found numerous fairy 

 rings formed by Psalliota campestris in grass-land near Yuma, 

 California ; and, in one instance, as is shown in Fig. 131, they 

 observed several Mushroom rings enclosed by a much larger ring 

 formed by the mycelium of Calvatia cyathiformis. Psalliota arvensis 

 sometimes also produces rings, and a good illustration of such a 

 ring occurring in the United States is given by Atkinson. 2 I have 

 seen similar rings at Malvern, England, many yards in diameter 

 and dotted with the unmistakable, huge, white-topped fruit-bodies 

 of the species in question. I have also observed some beautiful 

 fairy rings of Psalliota sylvicola, indicated by numerous fruit-bodies, 

 in a wood near Haslemere in England ; and Shantz and Piemeisel 3 

 found huge rings in eastern California formed by the mycelium of 

 Psalliota tabularis (Fig. 130). It therefore appears that, under 

 suitable conditions, there is a tendency for the formation of fairy 

 rings in several species of the genus Psalliota. There can be no 

 doubt that the mycelium of the fairy rings of Psalliota campestris 

 is perennial and that it may live on for a number of years producing 

 fruit-bodies annually. In this respect the vegetative part of the 

 fungus is analogous to the creeping rhizomes of many Gramineae, 

 Liliaceae, etc., which also have a perennial existence and serve as 

 a basis for the annual production of a new crop of aerial shoots, 

 flowers, and seeds. 



In general, in a fairy ring occurring in a field there is usually an 

 outer stimulated zone of green plants, a central more or less bare 

 zone, and an inner somewhat wider stimulated zone, the stimula- 

 tion making itself apparent in the increased height and greater 

 greenness of the vegetation. According to Shantz and Piemeisel, 



1 H. L. Shantz and R. L. Piemeisel, " Fungus Fairy Rings in Eastern Colorado 

 and their Effect on Vegetation," Journ. of Agri. Research, vol. xi, 1917. 



2 G. F. Atkinson, Studies of American Fungi, Mushrooms, edible, poisonous, 

 etc., Ithaca, edition 2, 1901, Fig. 18. p. 20. 



3 Shantz and Piemeisel. foe. cit. 



