Chlorophyllum molybditesChlorophyllum molybdites is very common in lawns and garden beds, during wet periods of spring, summer and autumn, occurring in groups or fairy rings. The large caps, 10-30cm in diameter, are whitish to brown, broadly conical often with margins slightly upturned, and covered with concentric circles of pinkish-brown to chocolate-brown scales. The centre of the cap is entirely brown. The gills are free from the stem, white at first, becoming greenish when the spores mature. The base of the stem is slightly swollen whilst a prominent and movable white or brownish ring with a fringed margin is present on the stem closer to the cap. This species is easily mistaken for “edible” mushrooms and smells and tastes “mushroomy”. The most obvious feature is the greenish gills of mature caps.
The major difference between Chlorophyllum and Lepiota is that Chlorophyllum develops green tinted spores and a green spore print. In older specimens the gills often turn green also (hence the name chloro=green, phyllum=gills). However, often the spores take a while to mature and may even appear to be white as in Lepiota! There was a poisoning some years back in which a famous mycologist searched the entire fruiting body that had poisoned someone and could only find *one* green spore. Symptoms of Chlorophyllum molybdites poisoning are mostly gastrointestinal in nature. According to Dennis Benjamin (Mushrooms: poisonings and panaceas, 1995, W.H. Freeman and Company, 422 pp.) "in some individuals the gastrointestinal syndrome, which occurs about 1-3 hours after the meal, can be very severe, especially the colicky abdominal pain, which can mimic that of a 'surgical' abdomen. Symptoms persist for up to six hours, and even longer in a few patients. Nausea, vomiting and diarrhea complete the picture. The diarrhea can be explosive in nature and become bloody." You probably won't die from eating this mushroom (although there is one recorded fatality involving a child), but it's certainly not a pleasant dining experience.