Nutrients required by the fungus are depleted from where it has grown, so the ring can proceed only in one direction, outwards, forming the inevitable ring. The lusher grass just forward of the front is thought to be due to release of excess ammonia by the advancing hyphae, making nitrogen available to the grass. Rings grow indefinitely but break up and become hard to recognise. They grow at an average of about 12.5 cm radius a year. Most records range from 8 to 34 cm.
Growth depends on species, soil and weather.
The Stinkhorn Finally, stories about the stinkhorn, Phallus impudicus , abound. There are endless stories about this obvious fertility symbol but one particularly seems to deserve telling. Armed with a basket and a pointed black stick, and wearing a special hunting cloak and gloves, she would sniff her way round the wood, pausing here and there, her nostrils twitching when she caught a whiff of her prey. Then with a deadly pounce she would fall upon her victim and poke his putrid carcase into her basket. But most surprising of all is the fact that Aunt Etty was none other than the eldest daughter of the great Charles Darwin.