THE FAIRY RING FUNGUS AN INDIRECT FERTILIZER 



TO GRASS. 



By Byron D. Halstcd. 



M 



Y attention has been called to the interesting article upon ' ' The 



Fairy-Ring Mushroom " by Professor Coville in the December 



issue of The Plant World, and particularly to the closing 



paragraph, where he asks more questions than most readers 



can answer. It is my pleasure to attempt to reply to only one of these, 



but not without the fear of thereby suggesting other questions waiting 



for answers. 



The presence of the Marasmius undoubtedly has a marked effect 

 upon the growth of the grass, resulting in the ring of "luxuriant 

 dark green grass. " These fairy rings are most strikingly evident in 

 rich turf, as remarked by Professor Coville in the opening paragraphs 

 of his paper. This "richness" means that there is an abundance of 

 accumulated organic matter, largely the product of the several years 

 during which the land has been in sod. Fungi generally are humus 

 feeders, and this is particularly true of the larger forms like the 

 mushrooms and toadstools of which the Marasmius is a fair type. The 

 vegetative hyphse of these fungi are better able to feed upon these 

 organic compounds than the higher plants that are accustomed to 

 make their food out of the inorganic substances of soil and atmosphere 

 by the aid of the sunlight and in the chlorophyll granules. 



The fairy-ring fungus, in short, acts as a reducing agent, break- 

 ing up the organic compounds in the turf and, while using a portion 

 for its own growth, quickly perishes, leaving the grass to avail itself of 

 the compounds set free. 



The ring of grass flourishes noticeably upon this " refuse," so to 

 speak, of the mushroom and soon exhausts the surplus. On this ac- 

 count the portion within the "charmed circle" is even poorer than 

 without, and for that reason the ring widens from year to year, the 

 fungus reaching toward the greater food supply and the more vigorous 

 grass following closely because of the excess of available food result- 

 ing from the destructive growth of the mushroom upon the accumu- 

 lated soil humus. 



The ring is an interesting manifestation of two widely different 

 methods of nutrition of very unlike but associated plants. A chloro- 

 phylless saprophyte in the one case finds a suitable place for growth 

 in the rich turf and takes from it the sustenance it requires, rendering- 

 it less fit for its own kind, and therefore marches slowly on and out- 



