PSALLIOTA CAMPESTRIS 363 



lost their turgidity. The microtome method of making preparations 

 is, as everybody knows, of the highest value for certain kinds of 

 research, especially for cytology ; but, for my purposes, it proved 

 quite unsuitable. I am inclined to believe that, if the microtome 

 had never been invented, the progress in our knowledge of the general 

 organisation of the hymenium of the Hymenomycetes would have 

 been much greater by now than it actually is. The first successful 

 investigators of the hymenium, such as Leveille, Berkeley, and 

 Schmitz, who flourished a century ago, studied their material in 

 the living condition. My own work is in continuity with theirs. 

 Occurrence of the Fruit-bodies. Fairy Rings. The fruit- 

 bodies of Psalliota campestris, the Common Mushroom, occur more 

 especially in pastures and other grassy places, where the mycelium 

 apparently feeds upon organic debris consisting of the subterranean 

 organs of grasses and perhaps other herbs, which are present in the 

 turf. They also sometimes come up on lawns, in well-manured 

 gardens, and in beds rich in turf and rotted horse manure, such 

 as are used for growing tomatoes and cucumbers. In addition, 

 Mushrooms are grown on a very large scale on artificial beds made 

 of stable manure. In pastures, they usually occur singly and with- 

 out any regular order in respect to one another, but sometimes 

 they occur in so-called fairy rings (Fig. 130). Such rings I saw near 

 Banbury, England, about the middle of August, in a hay-field 

 which had been mown only a few weeks before. One of the 

 rings was 1 yard in diameter, two others 2 yards, and one 

 3 yards. There were also a number of incomplete rings. Each 

 ring consisted of a circular dark-green zone of grass from 

 8 inches to 1 foot across. From this zone both centrifugally and 

 centripetally the grass was of a normal lighter green colour. There 

 were several fruit-bodies coming up in each ring (cf. Fig. 131). 

 On making excavations, I found that the soil consisted of a stiff 

 red loam and that, just beneath the dark-green zone but nowhere 

 else, the mycelium, interlaced with roots and rhizomes, could 

 be traced downwards for a distance of 3 inches (cf. Figs. 132 

 and 133). From our general knowledge of fairy rings, we may 

 conclude that the mycelium had started its existence in the centre 

 of the ring, that it had grown centrifugally outwards each year, 



