A Grammatical Dictionary of Botanical Latin

trabeatus,-a,-um (adj.A), trabeus,-a,-um (adj.A): provided or furnished with a beam-like stripe; trabed [> L. trabea (s.f.I), the beam-like stripe on the robe of state for Roman dignitaries]; cf. sepiarius,-a,-um (adj.A).

NOTE: it is possible that this adjective as a botanical epithet often or usually refers to the wooden or ligneous substrate of fungi, and, rather than the Roman ‘trabea,-ae (s.f.I), it refers to trabs, gen.sg. trabis (s.f.III), q.v., a cut or prepared piece of wood, a plank, a piece of lumber or timber:

Agaricus trabeus; Chaetoporellus trabeus; Lenzites trabea, a mushroom that is zonate, but also which grows “usually on hardwoods and also on boards and wood in service” (Miller).

Gloeophyllum trabeum, as in the genus, grows on rotted wood, much as Gloephyllum sepiarium, which grows on wood.

Lenzites trabea, a mushroom that is zonate, but also which grows "usually on hardwoods and also on boards and wood in service" (Miller).