Also sometimes called cloud ear or elephant ear mushrooms. The most appetizing name, though, is on the package of the brand I buy: black fungus. Yum. Just the sound of it makes you salivate, doesn't it?
Whole dried mushrooms of this genus - whatever you call them in English - are up to 1 inch in diameter, very thin, and black on the top side and dark grey on the bottom. The stems are quite tough when they're reconstituted, so I recommend discarding them. I usually buy these mushrooms dried and already cut up into strips, which is convenient, since I would be slicing them up anyway.
I don't find them to have much flavour; to me, they're nice for their colour and texture, which is kind of crunchy. Their blackness adds a nice contrast to the bright colours of a fresh spring roll, while their crunch is a welcome addition to, say, a vegetarian stir fry based around fresh mushrooms, which can become soft and almost slimy when cooked.
I also don't find them to have much of a hallucinogenic effect, and this is not the first time I've noticed that foods which I seem immune to have this effect on others. I wonder what these people have that I don't. An idiosyncratic chemical make-up? A low tolerance for things psychotropic? A fertile imagination? Who knows? And, if I had it, would it be a curse or a blessing?