UPDATE1-Blackstone appoints new CFO

(Adds details from Merrill Lynch internal memo paragraphs 4-5)

NEW YORK, June 9 (Reuters) - Private equity firm Blackstone Group (BX.N) said on Monday it hired Laurence Tosi from Merrill Lynch & Co MER.N to be Chief Financial Officer.

Michael Puglisi, Blackstone's current Chief Financial Officer, will remain a member of senior management, Blackstone said in a statement.

Tosi, most recently Chief Operating Officer for the Global Markets and Investment Banking Group of Merrill Lynch, is expected to take up his position after the summer, Blackstone said in a statement.

Merrill Lynch's chief operating officer Gregory Fleming said in an internal e-mail dated June 9 that Tosi was leaving. He wrote that Tosi was eager to take on a "new challenge" at this stage in his career.

Tosi joined Merrill Lynch in July 1999 as head of Business Development for the Global Markets and Investment Banking division and held a number of management roles of increasing responsibility and scale, Fleming wrote in the memo. (Reporting by Megan Davies)