Collybia tuberosa, commonly known as the lentil shanklet or the appleseed coincap, is an inedible species of fungus in the Tricholomataceae family, and the type species of the genus Collybia. Like the two other members of its genus, it lives on the decomposing remains of other fleshy mushrooms. The fungus produces small whitish fruit bodies with caps up to 1 cm (0.4 in) wide held by thin stems up to 5 cm (2.0 in) long. On the underside of the cap are closely spaced white gills that are broadly attached to the stem. At the base of the stem, embedded in the substrate is a small reddish-brown sclerotium that somewhat resembles an apple seed. The appearance of the sclerotium distinguishes it from the other two species of Collybia, which are otherwise very similar in overall appearance. C. tube