In mycology, “hypogean” describes fungi whose entire life cycle, including the development of fruiting bodies, occurs underground. Truffles, a well-known example of hypogean fungi, exemplify this underground habitat.
Sources
Researchgate – Fungi in Hypogean Environment: Bioprospection Perspective 
Natur & Kultur – Unusual Edible Mushrooms by Oliver Karlöf
April 2023, TÄNKOM | Revised February 2024 RETHINK
