Mushrooms are a type of fungus, and are not a plant. They come in a variety of sizes and colours. Some mushrooms are edible, but others are poisonous - poisonous mushrooms are often called toadstools. The top part of a mushroom is called the cap and the stem at the bottom is called the stalk. Mushrooms reproduce in a similar way to ferns. They grow spores in gills under the cap, which gradually opens from a ball to a disc as the mushroom matures. Some mushrooms release their spores in an explosive puff. Spores look like fine black dust.