Wall Street up on "buy the dip"

NEW YORK (Reuters) - Stocks rose on Tuesday after opening lower on weak economic data, with investors saying the data bolsters expectations the Fed will pump more money into the economy, which would support equities.

The S&P 500 has risen about 9 percent so far in September, making it one of the best months for the index in 20 years.

Some of the strength in equities "is related to the fact the Fed's been signaling they're going to be easy and some of the short-term economic data probably doesn't matter that much," said Perry Piazza, director of investment strategy at Contango Capital Advisors in San Francisco.

"Everybody expected seasonal weakness in September and they're not getting it so they're forced to hop on board the rally," he said. "People are buying dips."

U.S. Treasury debt prices also rose, as the weaker-than expected data increased expectations that the Fed will give the economy more support.

But the recent rally in bonds could be a bubble, Byron Wien, the vice chairman of Blackstone Advisory Partners, told Reuters Insider. He sees stocks moving higher, with little chance of another recession. http://link.reuters.com/nyn74p

The Dow Jones industrial average gained 55.10 points, or 0.51 percent, to 10,867.14. The Standard & Poor's 500 rose 5.39 points, or 0.47 percent, to 1,147.55. The Nasdaq Composite added 9.24 points, or 0.39 percent, to 2,379.01.

Walgreen Co , the biggest U.S. drugstore chain, reported higher-than-expected quarterly earnings, helped by strong prescription drug sales. Its shares jumped 12.3 percent to $33.95.

Continuing the spurt of recent M&A activity, Endo Pharmaceuticals Holdings Inc will buy private generics maker Qualitest Pharmaceuticals for about $1.2 billion, marking its second deal in as many months. Endo shares advanced 8.4 percent to $33.17.

September data showed U.S. consumer confidence fell to its lowest level since February, underscoring lingering worries about the strength of the economic recovery, while home prices dipped in July.

Shares of Apple Inc slid as much as 5.6 percent on rumors its No. 2 executive was departing for Hewlett-Packard Co , but the stock recovered as analysts dismissed the speculation.

Representatives from Apple and Hewlett-Packard declined to comment. Apple shares shed 1 percent to $288.30 and HP rose 1.1 percent to $41.72.

(Reporting by Rodrigo Campos; Editing by Jan Paschal)