The senior member of the Senate Warren G. Magnuson (D-Wash.), was in tears, but it had nothing to do with the sad story of the pecan planter's plaint.

They were winding up the 96th Congress last night in a way that Magnuson, defeated last month after coming here in 1944, would have to find poetically proper.

The last big bill of this Congress, the continuing appropriation to keep many government agencies afloat after Monday, was hopelessly caught in a swamp of despair and confusion.

Senate conferees, led by Magnuson, had seen their handiwork go down the tubes, and with it the congressional pay raise that had been inserted literally by dark of night on Friday.

Majority Leader Robert C. Byrd (D-W.Va.), after the Senate rejected the conference report, found a way to resurrect it without the pay boost for legislators and top-level civil servants.

They bounced the bill back to the House, which earlier and adroitly had found a way to approve the pay raise without a roll-call vote. Then the Senate tinkered with other pending business into late evening.

After Magnuson's appropriations bill was sent to the other side of the Capitol, the 75-year-old chairman stood and said, "I bid you fond adieu."

Every senator rose and applauded in tribute to the departing dean. The applause was long and warm. Magnuson sat in the first seat, front row, crying.

Now about those pecans, which is really, in microcosm, the story of the last hours of every Congress -- a little amendment helping folks at home that legislators love to slide through when eyes are averted.

Sen. Howell Heflin (D-Ala.) was proposing to give a $10-per-tree tax credit to every pecan grower trying to rebuild his groves after the devastation of a hurricane last year.

The House Ways and Means Committee had no hearing on it. The Carter administration opposed it. The Senate Finance Committee rejected it. But Heflin wasn't giving up.

He took his cue from Byrd, who announced that a bill was being kept around last night for use as "a vehicle" to which senators could attach special little tax goodies they were carrying around in coat pockets.

As soon as Heflin's praline came up, Sen. Howard Metzenbaum (D-Ohio) objected to its consideration. "You could probably write a book about what I don't know about pecan trees," he said, "but I do know about tax laws."

Threatening to filibuster the pecan amendment, Metzenbaum's point was made. Heflin withdrew and sat down.

Historians may look back someday and decide that Metzenbaum, a lean, gray-haired millionaire from Cleveland, was the closest thing to a Horatio at the bridge of the 96th Congress.

All during the last week, Metzenbaum and his staff kept an eye on the Senate floor and, with his threat to filibuster, had stopped a passel of special-interest tax bills in their tracks.

The Ohio Democrat had put a "hold" on 20 different tax measures and he forced the elimination of a number of proposals that would have drained the Treasury of billions -- yes, billions -- of dollars of tax revenue.

One amendment alone, proposed by Sen. William L. Armstrong (R-Colo.), carried a $2 billion price tag. It would have given corporations a huge depreciation tax writeoff. He dropped it under threat of a Metzenbaum tongue-lashing.

"I don't consider it heroics in any sense," Metzenbaum said last night, "but I just don't want any garbage going through here in the final days. I don't want to see Santa Claus on the Senate floor."

Metzenbaum got burned two years ago and he made ready this time, vowing that he wouldn't again let undebated, unexplained amendments breeze through. His triumph became clear earlier yesterday when Finance Committee Chairman Russell B. Long (D-La.) got seven little tax bills passed on voice votes.

They got through after Long agreed to expunge the objectionable portions and Metzenbaum approved them.

There were a few other Horatios yesterday -- among them, Rep. Andy Jacobs Jr. (D-Ind.) -- trying to keep track of the pea and the shells.

In the House, Jacobs objected to -- and stopped -- an amendment permitting tax-free mortgage bonds to be issued in San Bernardino, Calif., to help fire-disaster victims. "Two dollars out of every three go to the brokers," Jacobs said. "Everybody listens when E. F. Glutton speaks."

This Congress stands in recess. Or does it?