THE PLANT WORLD 207 



From my own observations I could assign a no more reasonable 

 explanation, since during six years of study I not only found many of 

 the large puff-balls, but also several of the smaller kinds showing a 

 decided preference for these dark green areas, though by no means 

 confined to them. Five years ago on one of my first field excursions at 

 Takoma Park, two large " rings " were found, and growing in them a 

 great number of one of the common large puff-balls of that region, 

 forming almost complete circles near the outer margin. These two 

 rings were under observation for three j^ears, and during that time not 

 only large but small puff-balls and also several species of gill-bearing 

 fungi were found in them, such as Galera tenera, Mm-asmiiis oreades, 

 Agaricus campe.stris, A. suhrnfesceus, and A. kemervidorhis. These spe- 

 cies of fungi were found in the surrounding meadow as well, but showed 

 always a decided preference for the rings. Three years ago it was 

 proven beyond a doubt that these rings were made by the growth of 

 Lepiota Iforgavi, Other rings of a similar nature were also found, and 

 one of them, which was illustrated in a recent Bulletin sent out by the 

 Department of Agriculture, during a year of observation showed a sim- 

 ilar disposition to encourage the more luxuriant growth of other species 

 of fungi that occurred elsewhere in the surrounding field. 



The crowning surprise was reserved for this year. When riding 

 in the outskirts of the city of Brookings on October 9th, I found grow- 

 ing in great abundance a large species of Trlcholoma (which for lack of 

 literature I am unable to name), and grovsdng too in such a manner as 

 to leave no doubt that this was the fungus that originally caused the 

 ring. The same fungus was found in other rings wherever the ground 

 remained undisturbed by the plow. In one place one was seen as an 

 almost perfect hemisphere, the other half of the ring having been made 

 into a lawn. In all cases the mushrooms were crowded to the extreme 

 outer edge of the ring, and grew so closely together that thej' seemed 

 to be piled on each other, making in many places almost complete 

 chains of shining white caps often six inches in diameter, surrounding 

 the darker area inside. How so large a fungus could have escaped 

 notice in a country where a fungus having a pileus over three inches in 

 diameter is indeed a rarity, is a mj^stery that is hard to explain. 

 Though the unusually moist autumn may account in a measure for the 

 large size of the caps, the fact remains that the growth under anj^ cir- 

 cumstances must be conspicuous. An interesting question is also 

 raised as to the effect the growth and decay of these robust species 

 that originally cause the rings may have in promoting the growth of 

 other species of fungi. 



Brookings, South Dakota. 



