CIRCE
The shamrock (and by extension the color green) was the emblem of the Irish Volunteers in the era of Grattan's Parliament in the 18c., and became an emblem of rebellion in the 19c. It was usually worn in the hat. Queen Victoria forbid such displays by members of her regiments. 'The Wearing of the Green' became a symbol of support for Irish independence. The song by this title is an anonymous street ballad dating to 1798, often attributed to Dion Boucicault (1822 - 1890) who published it. Bloom is showing his green socks to confirm that he is a worthy successor to Parnell. Ironically, Parnell hated the color green.
