In ch. 51, Lydia "was sure [Wickham] would kill more birds on the first of September than anybody else in the country." What was the significance of September 1st - the opening day of the hunting season?

When Lydia describes her wedding day to Elizabeth, she says "Just as the carriage came to the door, my uncle was called away upon business to that horrid man, Mr. Stone." Are we supposed to know who Mr. Stone is, or is he just a business associate of Mr. Gardiner's whose name has surprisingly remained in Lydia's memory?