Writing and speaking are such vulgar forms of communication, really, but they have to suffice for those who cannot tap dance. Those who can tap dance have got it made. They're the chosen. When the Martians finally arrive here, we should send forth the tap dancers to greet them.

Most of the best tap dancers have been black and have passed along steps from one generation to another. This is what is commemorated and given a warm homage tonight in "No Maps on My Taps," a public TV tapumentary at 10 on Channel 26. George T. Nierenberg's one-hour film is a fiesta of fidgety feet, sly asides, dance Americana and heartfelt hoofing.

The program, fourth of this season's "Non Fiction Television" shows from New York's Channel 13, features three active custodians of the culture -- Sandman Sims, Chuch Green and Bunny Briggs -- and ends with them competing in a three-way challenge dance at Small's Paradise Club in Harlem. Lionel Hampton leads the band.

Sims is the most vocal of the group. He remembers how Green went through about a 15-year bad spell that followed the breakup of Chuck and Chuckles, a celebrated dance act, but he says of his friend that "you'd have to kill this guy to stop him from dancin'." Dutifully and wishfully, Sims tries to pass on the steps and the mythology to his own son.

When he was a boy, Sims recalls, he and his friends would trade steps on the street while they watched the white kids trot off to dancing school. Ah yes -- all the difference in the world. Briggs, who has soft round features and amazingly tolerant eyes, is the most affable of the performers. He is seen as a kid in a 1933 film clip, dancing his socks off on what is supposed to be a front porch.

"I think God meant for me to dance, 'cause I was dancin' when I was 2," one of them says, and another analyzes succinctly the longevity and appeal of this idiomatic form of artful articulation: "We outlast all the horses - - -."

John W. Bubbles can be glimpsed briefly in a scene from an old, black-produced motion picture. He then materializes in the present, talking and reminiscing on the telephone. The tapsters compare themselves to championship fighters and kibitz about the old days with ingratiating good humor tempered by a sadness over eras ended.

All labors of love should work out as lovely and lovingly as this film.