Absent

Why did they give up the stem?

As M.Ya. Zerova notes, the main purpose of a stem is to lift the mushroom above the ground so the wind can carry its spores. But if a fungus is already growing on a tree trunk two meters up, there's no point spending resources on building a stem — it's high enough as it is. The cap simply grows onto the bark, forming a sturdy horizontal shelf whose gills or tubes face straight down.

The main stemless fungi

The largest group of sessile fungi is the polypores (Polyporaceae). Their fruit bodies are often shaped like a horse's hoof, a half-circle or a burl.

1. Tinder fungus (Fomes fomentarius): The classic gray "hoof" on the trunks of old birches. It has no stem at all. It is fixed rock-solid to the bark and is very hard and woody.

2. Splitgill (Schizophyllum commune): A very small, widespread fungus that grows on dead branches. It looks like tiny hairy gray shells with no stems. Interestingly, its gills can split in two in dry weather.

3. Beefsteak fungus (Fistulina hepatica): This unique edible fungus grows on oaks and resembles a piece of raw liver in shape and color. It has no stem; it attaches to the trunk by its narrowed side (sometimes with a very short pseudo-root).

Balls and stars

Besides wood-dwelling fungi, the gasteromycetes that grow on the ground also have no stems:

- Puffballs (Lycoperdon): Some species (the stump puffball, for example) have a small sterile base (a pseudostem), but no true stem — they're simply balls sitting on the substrate.

- Earthstars (Geastrum): They are ball-shaped, and their outer skin splits open into a star that stays lying on the ground without any stem.