Oct. 29,1917 
Fungus Fairy Rings 
215 
annual increase in the rings and found it to be from 8 inches to 2 feet 
per year. 
Thomas (1905) reported on a ring that had been studied especially as to 
its outward increase for the period from 1896 to 1905. This ring was 
formed by Hydnum suaveolens. In 1896 the ring was nearly complete, 
but was never complete after that time and only during the years 1901, 
1902, and 1905 was there any appreciable increase in outward growth. 
The average increase of the radius for the period was found to be 23 cm. 
From this the age of the ring was calculated to be about 45 years. 
Ballion (1906) found an increase in the radius of a ring to be 12 cm. 
during one year, but said the increase was very irregular. The advance 
was said to be most rapid when the ring was young. 
Coulter, Barnes, and Cowles (1911, p. 807) mention a colony of Hydnum 
suaveolens which advanced from 9 to 11 meters in a period of nine 
years. The age of the colony was estimated to be about 45 years. 
Bayliss (1911) found the maximum increase of a ring of Marasmius 
oreades to be 13^ inches per year, and the minimum increase 3 inches. 
She thought rings might extend for 50 or even 100 years. 
Very little data are available on the rate of advance of fairy rings in 
eastern Colorado. Doubtless it is very unequal, and during dry years 
little, if any, advance is made. During moist years, such as 1915, the rings 
make a very decided advance. 
The first crop of Agaricus tabularis usually occurred near the inner edge 
of the outer stimulated zone (zone 4, fig. 3). The second crop, which in 
1915 occurred two months later, had advanced an additional 8 to 30 cm. 
(fig. 11). 
It is often evident from the old fruiting bodies which have remained 
in place that the advance is approximately the same for the first as for 
the second crop. But the rings fruit only during the exceptionally wet 
years. If it is assumed from these observations that the amount of. 
advance for each crop is approximately 30 cm., we may estimate the age 
of the rings on the basis of the records of the last 10 years. Four crops 
have been produced in 10 years, which would correspond to an advance 
of 120 cm. in this period of time. From observations of the rings during 
this period these estimates would seem to be approximately correct. 
On this basis the average yearly advance would be about 12 cm. A 
ring 60 meters in diameter would be approximately 250 years old. In 
the southern portion of the area shown on the map (fig. 2) a large num¬ 
ber of small or fragmentary rings are roughly arranged in the form of 
two still larger rings. If these fragments have had a common origin, 
which seems a correct assumption, the age of these large fragmented rings 
would be approximately 600 years. 
The rate of advance of the Calvatia cyathiformis ring is about the same 
as that of the Agaricus tabularis ring during periods especially favorable 
