Clitocybe is a large and important genus of gilled mushrooms, which are saprophytic and can be found on the ground both in grassland and woodland. There are some choice edibles in the genus, and one or two potentially lethal toxic species. The genus has recently been expanded on the basis of molecular testing as to include the whole of the old genus of Lepista – the blewits.
Wood blewits (Clitocybe nuda) are a very common feature of late autumn. Just as some of the other species are fading away, this species usually turns up and often in generous quantities. Regardless of its fame and popularity, it is not the easiest to identify safely. It is also particularly dodgy to rely on internet identifications of this species, because it closely resembles several rather variable Cortinarius species of dubious edibility/toxicity. The easiest way to tell them apart is to use your nose – wood blewits smell strongly of flowers or perfume. If you have no sense of smell (and one of my recent students proved this to me by not being able smell Tricholoma sulphureum, which absolutely stinks of gunpowder) then you might be advised to steer clear of this one, or get somebody else to check before you eat it.
There are several other edible blewits, but the rest of the genus is decidedly tricky, and not for beginners. The first species you need to know if you’re thinking about eating clitocybes is C. rivulosa/dealbata.
Mycologists will argue whether there is one species or two, but from a foraging point of view your just need to know they/it are/is not to go anywhere near your mouth, because it can cause heart and/or breathing failure. Very common, this species has a habit of growing in rings in exactly the same places (sometimes right next to each other, at the same time) as a well-known edible species called a fairy ring mushroom (Marasmius oreades.) It could also easily be mistaken for an edible waxcap, and is a dead-ringer for a very good edible species called the miller (Clitopilus prunulus.) The latter grows near trees and never in rings, but the similarity is close enough to mean that the miller should be left to experienced fungi foragers; you must familiarise yourself with the dangerous clitocybes first.
Warning over with, there’s also some other edible clitocybes, most common of which is Trooping Funnel (Clitocybe geotropa.) This mushroom is a bit tough (or “meaty” if you’re being more generous), but it is very common, and large enough not be confused with any of its smaller, dangerous relatives. It is very easily confused with an even bigger species (giant funnel – Leucopaxillus giganteus) but this is also edible. They are practically indistinguishable when young, which is the best time to eat them.