In fall, supermarket displays give mushrooms, or kinoko, pride of place, piling them high in glorious abundance. Though of course mushrooms are available all year round, there are certain varieties such as the high-priced matsutake that only come into season in the autumn, and no matter what variety, mushrooms seem especially suited to cold-weather dishes like hot pots (nabe) and stews (shichuu).
There are many more types of mushrooms commonly used in Japan than in the U.S. Above, there are brown enoki-dake in the wicker basket and maitake spread out on the table. The word kinoko, which means "child of tree," covers all mushrooms, while the button mushrooms that are standard back home, but pretty exotic here, are called "mashiruum" in Japanese. A few Asian mushrooms, like the shiitake at the top, have made their way into the American vocabulary, but most of the others would probably be unfamiliar. In fact, the shiitake mushrooms I've seen in the U.S. don't even look much like the big, fat ones here, which you can see both whole and sliced on the left in the photo below.
The ones in the middle above are eringi, which have a lot less flavor than most Asian mushrooms but are very chewy and seem to shrink less than other mushrooms do when cooked. They're often added to stews. I also love their shape, which just looks so ... mushroomy. On the right are white enoki, much more common than the brown ones. White or brown, enoki have a slightly sour flavor and a distinctive smell. Their long, skinny stems make them especially fun to eat - sort of like spaghetti. Shiitake (which is pronounced with the emphasis on the first syllable, not on the "ta" as it's usually said in English) are the most meaty-flavored of the Asian mushrooms, and used for the greatest variety of dishes, from stews to mushroom-rice to side dishes served on their own.