Final answer:
In the Aeneid, the elm tree Aeneas sees as he enters the underworld is a significant symbol, representing bad omens and housing dreams, and contributes to the setting's dark atmosphere alongside hybrids and monsters of Greek mythology.
Step-by-step explanation:
In Virgil's epic poem, the Aeneid, as Aeneas enters the underworld, he encounters an elm tree that is described as dark and enormous in size, with the ability to house haunting abstractions and empty dreams. The elm is signified as an arbor infelix, a type of tree that is known not to bear fruit, and is therefore considered a symbol of bad omen, suitable for the setting of the underworld.
Its vast size corresponds with the Roman emphasis on the enormous scale of the underworld, a concept often highlighted in Roman poetry. The elm's association with dreams and its presence at the entrance of the underworld serve as a connection with the ancient idea of the underworld being an enormous pitcher with a narrow opening, a concept exemplified in the expression in faucibus Orci, meaning 'in the jaws of Orcus'.
Furthermore, this elm tree is associated with various hybrids and monsters from Greek mythology, creating an environment that adds to the eerie atmosphere of the entrance of the underworld. The nod towards Orphic and Stoic traditions in Virgil's depiction of the underworld is made evident by the incorporation of elements like the Golden Bough, the Sibyl acting as a travel guide, the emphasis on the river Lethe, and the overall construction of this underworld space, which includes places such as Elysium and Tartarus.
Thus, the elm tree represents the complex blend of Greek influence, Roman tradition, and older Orphic material that Virgil wove into his literary creation.