| Mushrooms are fungi, which are plants that lack the chemical that makes other plants green (among other things). Mushrooms are specifically of the class Basidiomycetes. These are the basic features of a mature mushroom, here shown on the highly poisonous Amanita. |  |
| Many types of mushrooms |  |
| Agaricus campestris, a common agaric |  |
| A typical young mushroom of the subdivision Basidiomycotina, known as a "button" at this age |  |
| That same mushroom a few days later |  |
