An undercover effort to elect a dissident stockholder to the board of directors of American Realty Trust and a potential takeover bid have pushed up the price of the Arlington company's stock by nearly 50 percent in the last two months.

The bid for a board seat was blocked by American Realty's management last week, but the dissidents say they are continuing to buy stock in the Virginia company and could make another effort to gain a larger voice in its management. c

Reports filed with the Securities and Exchange Commission show the dissident group, headed by present board member Brent D. Baird, is already American Realty's largest stockholder, controlling more than 7 percent of the company's shares.

Baird has reported his efforts to increase his control over American Realty to the SEC as required by law, but the company's management so far has disclosed none of the behind-the-scenes maneuvering to the shareholders, most of whom live in the Washington area. American Realty officials and business associates of Baird explained what has been happening in interviews this week with The Washington Post.

The maneuvering and speculation about a possible takeover of the company produced over-the-counter trading in American Realty shares and pushed their price from about $3 earlier this summer to a current asking price $4.75.

The activity began early in the summer when Baird, a New York investor who was named to American Realty's board a year ago after acquiring a large block of its stock, proposed that a Mississippi real estate man named Leland Speed be added to the board.

Baird, a major investor in both companies, also is a chairman of ICM Realty, a company whose shares are listed on the American exchange.

Speed's attempt to get onto the American Realty board was rebuffed by the company's chairman, 67-year-old Virginia businessman Joel Broyhill, setting off a quiet confrontation that ended about 10 days ago.

When Broyhill refused the seat to Speed, Baird retaliated by refusing to vote his stock at American's annual meeting. Like many small publicly owned companies, American Realty sometimes has trouble getting a quorum of its stockholders to show up either in person or by proxy at its meeting. With Baird withholding his votes, Broyhill was forced to postpone the stockholders' session twice because he could not get a maority of the shares represented.

After mailing several letters to stockholders asking them to send in votes in favor of American's old board of directors, Broyhill last week finally got 54 percent of the vote and was able to hold the meeting and re-elect the board.

None of the management letters to shareholders mentioned Baird's attempt to add Speed to the board, and neither Baird nor Speed formally campaigned for the seat.

In a telephone interview, Speed said Broyhill "kind of hurt my feelings" by refusing him the seat on American Realty's board. He said he and his associates are continuing to invest in the company's stock but would not comment on reports they might make an offer to seek control of the company.

Speed said he is president of Eastover and Citizens Growth Properties of Jackson, Miss., and a third real estate trust called Parkway Corp. "Every one of our companies has done very well," he added without directly criticizing Broyhill's management of American Realty.

Speed would not discuss his plans for the Arlington firm. "We invest in real estate," he said. "Sometimes we invest by buying stocks in REITs [real estate investment trusts]."

American Realty was organized as a real estate investment trust, which qualified for special income tax treatment but gave up its REIT status five years ago when it took over active management of some properties.

The firm is considered an attractive investment because the real estate it owns is believed to be worth substantially more than what the stock is selling for. The real estate is carried on American's books at a depreciated value of about $3.80 a share but in reality could be worth as much as $10 to $12, according to investors familiar with the holdings.

"A number of people have looked at the value of the assets and contemplated an offer," said John F. Rutledge, assistant to the president and the person responsible for day-to-day operations of the company.

The talks have not produced any offers for the company, Rutledge added. He confirmed that Baird's group is one of two which have been buying American Realty shares lately. a New York firm called Deltec owns about 100,000 shares, a little less than 5 percent holding that requires a report to the SEC.

Rutledge said investors who have been buying American Realty stock "are intrested in one of two things . . . . They see the value of the properties and want to buy it at a nice price or they want to take over the trust."

American Realty is negotiating to sell two major properties, the Hospitaliy House hotel in Arlington and a vacant six-acre site downtown Atlanta next to that city's Hyatt Regency hotel.

Hospitality Management Co. Inc. has signed a contract to buy the local property for $8.7 million, or $6.7 million more than the value on American Realty's books. An Atlanta buyer earlier this year offered $11 million for the block there that American Realty values at $5 million; that deal fell through, but is being renegotiated, Rutledge said.