Tooth fungi are a relatively small polyphyletic group of fungi whose mushroom bears its spores on a hymenium - a layer of "mother cells" - Although many tooth fungi are hard and inedible, some are prized both for their flavor and their ease of identification, such as Hericium erinaceus, the "bearded tooth mushroom". Others, such as Sarcodon imbricatus are edible but bitter. Still other species, though not edible, find use in the production of natural dyes.