Bass Has 5.6% Stake in Houghton Mifflin

The last major independent book publishing company left after a wave of mergers became the center of takeover speculation Tuesday as the Robert M. Bass Group announced that it holds a 5.6% stake in Houghton Mifflin Co.

The old-line Boston publisher is considered the only pure book publishing company of any size that is independently owned.

It publishes school texts and general-interest books, and owns a valuable back list of titles.

The Bass Group reported in a disclosure statement that it holds an initial stake of 790,200 shares of the stock outstanding, saying it acquired the shares as an investment.

Directors control about 10% of the stock.

Houghton Mifflin’s shares closed up $8.875 at $45.25, in New York Stock Exchange trading.