A 45-foot-long cross of flowers in Warsaw's Victory Square has become a symbol of struggle between Poland's martial-law authorities and supporters of the suspended trade union movement Solidarity.

The cross was first built unofficially a year ago in honor of the late primate of Poland, Cardinal Stefan Wyszynski, who died on May 28, 1981. Laid out on the stone pavement, midway between the Tomb of the Unknown Soldier and the political directorate of the Ministry of Defense, it is an object of pilgrimage for thousands of Poles every day and a source of considerable irritation for the government.

Over the past month, the cross has been destroyed on three separate occasions by police who came in the middle of the night to sweep away the branches, flowers, and candles. Each time, however, it has been rebuilt within hours by groups of Warsaw residents. With each reincarnation, the cross seems to get more elaborate and magnificent--and draws ever larger crowds.

The self-appointed chief custodian of the cross is a slender 54-year-old woman, Eva Pilsudska. The monument has become something of an obsession for her: she spends up to 12 or 14 hours a day looking after it.

"For me it is a symbol of hope," said Pilsudska, trying to explain why the cross has assumed even greater significance since the imposition of martial law last December. "It is one of the few places in Poland where you can still feel like a Pole."

A young music student, who helps Pilsudska tend the cross, agreed that it has become more than simply a gesture of respect for Wyszynski, Poland's spiritual leader for more than three decades.

"This monument represents both the struggle of the nation and its present divisions," the student said as she pottered about the cross, clipping away branches and sticking fresh tulips and roses onto its sides. She asked not to be named for fear of police harassment.

Young people from nearby parishes who have collected money for flowers to lay on the cross frequently have their identity cards checked by police. Plainclothes officers are also believed to mingle with the crowds who flock around it.

Earlier this month, the cross was more than once the scene of tense confrontation between Solidarity supporters and the police. Groups of several hundred would begin singing hymns and patriotic songs interspersed with slogans like "democracy" and "freedom." Truckloads of police, supported by water cannon and armored personnel carriers, circled the site.

On one occasion, a police officer told the crowd through a bullhorn that only those praying would be allowed to stay. Whereupon, Pilsudska recalled, the entire crowd knelt down by the cross and prayed.

The authorities do not seem to know quite what to do about the cross. Technically it is an illegal object. But if they were determined to dismantle it permanently, authorities would have to mount a 24-hour guard. The chances are that a similar monument would then spring up somewhere else.

Most days, the atmosphere by the cross is relaxed. On a recent sunny afternoon, knots of people gathered around as some elderly women embellished it with the figures "600"--a reminder of the fact that this year is the 600th anniversary of the arrival in Poland of the Black Madonna of Czestochowa, the nation's most revered religious symbol.

Pilsudska explained that the first cross of flowers appeared in Victory Square on June 2, 1980, to commemorate the triumphant pilgrimage to Poland the year before by Polish-born Pope John Paul II.

The cross disappeared the same night.

A year later, the funeral for Wyszynski was held in Victory Square. His coffin stood on the same spot. Young people again laid flowers in the form of a cross--and this time Pilsudska suggested that it remain there until a permanent memorial to Wyszynski was built.

This was the heyday of Solidarity and, apart from the odd vandal, nobody interfered with the cross. For a brief period, according to Pilsudska, the honor guard marching to the Tomb of the Unknown Soldier from the Defense Ministry even broke into ceremonial goose step as it passed the site.

After the imposition of martial law on Dec. 13 last year, the cross started attracting more and more visitors, and it became a focus of protest against the suspension of many civil liberties and the internment of union activists.

The police removed the cross for the first time on the eve of May Day.

After being rebuilt, the cross was dismantled again on the night of May 8 prior to military ceremonies marking the end of World War II in Europe. This time, it reappeared within minutes of the end of the parade. Young people emerged as if from nowhere, laying flowers once again in the cordoned-off square.

Police took the cross away for the third time in the early hours of May 15.

A former editor, Pilsudska now divides her time between looking after the cross and looking after her 92-year-old mother.

As for the cross, she hopes the authorities will now leave it alone. "I think they are realizing it's a hopeless fight," she said.