Vincent Melzac, 70, the tough and controversial Washington collector, has transferred what he calls his "most important paintings" to the Smithsonian Institution's National Collection of Fine Arts.

The 26 abstract pictures involved in the transaction are together worth perhaps $2 million.

Ten of them -- a large, important Clyford Still of 1946, a 1961 Franz Kline, two Willem de Koonings, two Kenneth Nolands and four big canvasses by the late Morris Louis -- were bought by the museum for approximately $1 million. The money comes from the Smithsonian fund especially set aside for "outstanding" acquisitions.

Melzac gave the museum the 16 other pictures. Works by Howard Mehring, Gene Davis, Noland, Jules Olitski, Norman Bluhm, Paul Reed and a fine De Kooning from the early 1940s are among the pictures in the Melzac gift.

The daring of his buying -- and the quickness of his temper -- have made Melzac famous on the local scene. He was the first collector here to buy in depth the paintings of the Washington Color School. He also was the first chief executive of the Corcoran Gallery of Art to leave that high position following a fist fight. It took place in 1972 at a black-tie Corcoran opening, and it left Gene Baro, then the gallery's director, bleeding, in his own words, "like a stuck pig."

Melzac's reputation has long been sort of mixed. Though he has, in recent years, been generous to many Washington museums, the Corcoran among them, he was known as a hard barginer when he bought his art. And though as a collector he was ahead of his time -- he bought the Abstract Expressionists in the 1940s and the Washington Color Painters in the early 1960s -- Melzac made his money by catering to the vanilites and idiocies of American mass taste.

He used to franchise "charm schools." He also sold such television turkeys as "Rama of the Jungle."

He eventually acquired hundreds of abstract paintings. Yesterday he said, "I don't have many left."

"I have given the best of them to the National Collection. That way they'll stay together in this city, that was the whole idea. Some years ago I was offered a very handsome price, nearly $3 million, by Christie's of New York, but I didn't want my pictures to be dispersed at auction. I was born in Poland, and I'm grateful to this city and this country. I made my money here."

Melzac, who lives in Alexandria and raises Arabian horses on a farm in West Virginia, said yesterday that he was "through as a collector." The 16 paintings in his latest gift bring to 31 the number of pictures he has given to the National Collection. Most of the works involved in the transaction have been on a loan to that museum for the past few years.