The Olive Tree, by Italian naturalist Ulisse Aldrovandi (1522-1605). 
An olive branch has long been used as an offering of peace, even to this day. 
Virgil (70-10 BCE) in his Aeneid: 
 
"High on the stern Aeneas his stand,And held a branch of olive in his hand,While thus he spoke: “The Phrygians’ arms you see,Expelled from Troy, provoked in ItalyBy Latian foes, with war unjustly made;At first affianced, and at last betrayed.This message bear: The Trojans and their chiefBring holy peace, and beg the king’s relief.”

The Olive Tree, by Italian naturalist Ulisse Aldrovandi (1522-1605). 

An olive branch has long been used as an offering of peace, even to this day. 

Virgil (70-10 BCE) in his Aeneid

 

"High on the stern Aeneas his stand,
And held a branch of olive in his hand,
While thus he spoke: “The Phrygians’ arms you see,
Expelled from Troy, provoked in Italy
By Latian foes, with war unjustly made;
At first affianced, and at last betrayed.
This message bear: The Trojans and their chief
Bring holy peace, and beg the king’s relief.”