The day before, they had seen the bulldozers plow down the tall trees like a ball hitting bowling pins. They said they knew they could not stop the trees from going down or the new housing development from going up on their old hiking trail.

But they wanted to make it known, they said, that they did not like what they saw and did not want to see it happening in the future.

So, armed with paper signs and a cardboard "coffin" filled with tree branches, 20 children - aged 5 to 15 - from the Potomac Woods Park area in Rockville picketed yesterday in front of the new Potomac Springs housing development on Seven Locks Road. Construction of Potomac Springs, they said, has robbed them of a wooded area where they once played hide and seek and of a trail they used to get from their homes to the Rockville Mini Mall across Seven Locks Road.

Five-year-old Leslie Israel bounced up and down in her yellow bell-bottoms and a striped polo shirt, carrying a sign that said, "Trees, We Love You, Leslie." Her brother Benji, 15, said be learned all about nature in the special outdoor science class he attended earlier this summer on A Wallops Island in Virginia. Their friend John Sullivan, said his father who works for Energy Research and Development Administration, taught him about the environment.

"We're supposed to be the future rulers of the world, right?" asked Kim Kline, 12, a seventh-grader at Ritchie Park Elementary School. "And we know these houses are going to be for us when we get older. But Nobody asked us if we think it's good to build them."

Behind her stood the wooden skeletons and concrete foundations of homes under construction. The once grassy slope the youngsters used to play on is now, bacause the construction, a crater of mud.

When asked for comment, the sales representative for Potomac Springs said: "I think their parents put them up to it. Look at all these lovely trees." She pointed out the window of the sales trailer, which sits beside a grove of trees.

"We're really doing this for the younger kids" declared Caroline Cardullo, 15, who attends Thomas S. Wooton High School and said she wants to be and environmentalist.

"We (the older kids) have already enjoyed the woods that were here and the hiking trails," she said. "We can't stop this development from being built but we can maybe stop it from spreading."

The protest lasted about half an hour. Then a Montgomery County policeman came by and cautioned the youngsters to stay away from the heavily-traveled Seven Locks Road.