I was mystified to read of Gov. Martin O'Malley's 145 "green bag" appointments to various boards and commissions, but lo, such appointments in Maryland actually are taken to the state Senate in a green bag! Here's the history, courtesy of the Maryland State Archives, official custodians of the green bag.
Like many "historical" and "traditional" customs, this one seems to have been invented within living memory. No one is sure there was an actual green bag before 1951, and the current one dates from 1983, when I was an undergraduate.
I am reminded of the equally useful customs enforced by Sourdust and Barquentine, the father-and-son Masters of Ritual in Mervyn Peake's Gormenghast.