More than 250 persons eavesdropped yesterday as a dance critic and a ballet choreographer-director gossiped and told some of their favorite stories. b

Stories like this one from Olive Barnes, the dance and drama critic of the New York Post:

At a rehearsal of "Sleeping Beauty," Mikhall Baryshnikov kept admonishing the ballerina in Aurora's role to "do it like Margot." Someone wondered how Baryshnikov, at his age, ever could have seen Dame Margot Fonteyh perform on stage.

Then the Russian dancer told how, as a teen-ager, he had traveled 200 miles to see an amateur film of Fonteyn in the role and her movements were burned on his memory.

Barnes and Robert Joffrey, founder of the dance troupe that bears his name, chatted before microphones yesterday at the first of two "Wolf Trap and the Arts" lecture-luncheons at the Four Seasons Hotel in Georgetown.

Next Wednesday Sarah Caldwell, just appointed music director of Wolf Trap, will tell luncheon subscribers about plans for the 1980 10th anniversary season at Wolf Trap.

Mrs. John Crutcher, chairman for the luncheon series, admitted that the time and place for the series has been chosen with an eye for attracting men on their executive lunch time. Yesterday there was a good sprinkling of men in the audience.

The turnout to hear a dance critic and choreographer reflected one point made by both Barnes and Joffrey: The dance "explosion" of the last decade and half in the United States.

Sixteen dance tickets were sold in 1975 for each one sold in 1965 Barnes noted, and today, he estimated, the "16-to-1 figure certainly has doubled and probably tripled."

One of the factors in this increased interest in dance, Barnes said, has been television, which has brought about a "generation used to visual communication rather than verbal."

Joffrey, whose troupe will appear at Wolf Trap this summer, emphasized how young American ballet is when compared to a company like the Bolshoi with its 200 years of tradition.

In the 1930s and 1940s, Joffrey recalled that "if you danced, you were Russian," and native-born American dancers adopted Russian-sounding professional names.

Today Joffrey said, a list of the world's leading choreographers probably would be led by American names. Barnes agreed, hazarding the guess of "34 of 50."

As a choreographer, Joffrey conceded that it is the dancers who have the "muscular memory" of the roles that they originally created.Choreographers, he said, are always going off and creating new dances.

He told the story of trying to stage a Massine-choreographed waltz ballet and finding Massine of little help when the tone was wrong. Then, Joffrey recalled, Frederick Franklin, who had danced the ballet decades before, stepped in and said to Massine:

"What are you doing to the dance? You touch the floor, I danced it. I know. I remember what you told me then."