Final answer:
The mushroom in question is most likely the Agaricus bisporus, known as the white button mushroom, which is commonly sold in grocery stores and used on pizzas. It is commercially cultivated for sale but can also be found in the wild in Illinois.
Step-by-step explanation:
The mushroom being referred to in Illinois is likely the Agaricus bisporus, commonly known as the white button mushroom, pizza mushroom, Portabella, and Crimini. This species of mushroom is familiar to many because it is the commercial type sold in grocery stores and frequently found on pizzas. Agaricus bisporus is available in various forms: the classic button mushrooms, the brown Crimini versions, and the larger Portobello versions. These mushrooms are cultivated on a controlled medium and environment, such as caves or underground structures, to maintain constant temperatures and high humidities, which are ideal for their growth.
Agaricus bisporus can be found in the wild in fields or lawns, but commercially sold mushrooms are farmed. The cultivation of mushrooms like the morel and truffle, which are Ascomycetes, presents a more considerable challenge. Morels are particularly sought after and often command high prices due to their rarity and the difficulty in cultivating them. Morel collecting is a popular activity in spring, and these mushrooms are often found in forests, associated with specific trees or conditions following a fire.