#036: Mushroom Morphology: Earth Tongues
The term “Earth Tongue” refers to the tongue-shaped mushrooms in a few select genera: Geoglossum (literally “earth-tongue”), Trichoglossum, and Microglossum. These fungi all have tongue-shaped heads on a sterile stipe. The heads usually have a groove running down the center and two similarly-shaped lobes on either side. This morphology is somewhat reminiscent of a tongue, thus the name of the group. You’ll need a microscope for accurate identification of your earth tongue collection. If you have access to one, see the “Beginners Guide to Earth Tongues” (linked below*) for tips on microscopic examination. The key provided at the end of that article, however, was written for people in England and therefore may not be useful for American mushroom hunters. If you’re satisfied with identification down to genus only, then there are a couple things you can look for when sorting your collection. First, Geoglossum and Trichoglossum produce black mushrooms, while Microglossum produces olive green to brown mushrooms. Second, Trichoglossum species have a bristly stem.
Earth tongues are found from the summer through the fall. They usually fruit on the ground (often in or near patches of moss), but are sometimes found on decomposing wood. I once found an earth tongue embedded in the stipe of a larger bolete, which had apparently decided to fruit in exactly the same spot as the earth tongue. Recent studies of the three earth tongue genera have shown that they do not form a monophyletic group. According to Wikipedia (and supported by the authoritative, referenced articles), the genera Geoglossum and Trichoglossum (the genera that produce black earth tongues) are currently placed in the Phylum Ascomycota, Class Geoglossomycetes, Order Geoglossales, and family Geoglossaceae. Microglossum (which produces olive to brown mushrooms) was left in the Class Leotiomycetes.