Stocks in Citigroup fell a record 26 percent yesterday as concern grows over the future of what was once the nation’s largest bank. Citigroup shares have lost half their value this week even though the government injected $25 billion into the bank last month. Citigroup’s board is holding an emergency meeting today. The Wall Street Journal reports the board is considering selling off the entire company to another bank or to sell off parts of the firm. Earlier this week, Citigroup announced plans to lay off 52,000 workers.