Between us,"" poet/librarian/popular-historian Bontemps wrote to poet/ dramatist/folk-popularist Hughes in 1944, ""we oughta put the new generation on a new track""; and, sure enough, a youngster soon turned up with the name ""Langston Arna."" They were on their way to becoming the Grand Old Men of Negro Letters, these two kindred spirits and longtime collaborators who were so alike--in age (b. 1902), in mien, in middle-classness, even in attire--that they were often mistaken for one another. And for 40 years, from the 1920s Harlem Renaissance till Hughes' death in 1967, they exchanged news of their own work and kept tabs on the endeavors of fellow-blacks. . . . We find them, in 1931, with a story about Haitian children in the hands of an interested, querying publisher: ""Why not put in,"" says Hughes, ""the fine gentlemen with high colors and linen suits who work in the offices and shops; brown skin gentlemen with bushy heads and new watch chains of gold and shiny pointed shoes. . . if they want color."" Hughes is embarked, in 1955, on a ""book about Negro Heroes"": stick to warriors and adventurers, says Bontemps (citing some), and leave Joe Louis out. Children's books and lecturing were mainstays for both: Bontemps, though employed (by the Rosenwald Fund, as librarian of Fisk University), has a huge family to support; Hughes wants to write and only to write--most achingly, most crushingly, for the theater. (""It cripples your soul,"" he warns Bontemps--a sometime playwright and lyricist too--after the success of the K. Weill-L. Hughes Street Scene.) But the 500 letters have most to say about being black. Note is taken of each black debut (""Be sure to read""--says AB--""that remarkable piece by the 24-year-old colored kid in the current issue of Commentary. . . . His name is Baldwin"") and each black breakthrough (""Leontyne"" at the Met, Carl Rowan at the State Department); of the personal constraints (""Which downtown Cleveland hotel""--in 1945--""is courteous to Negroes?"") and the psychic costs. Scott Joplin's widow won't answer a letter: ""Perhaps she's afraid,"" Bontemps writes, that ""I'll say in the book that Scott died insane, as I understand he did! Colored will never have much history! They are too scared somebody will find out what they had to do for a living, etc."" For these two stalwarts, there is never a question of the value of ""chipping away at the color line""--on any front. The collection is abysmally edited: no explanatory headnotes--for which the introduction and terminal chronologies don't substitute; virtually no identification of persons; and a chronic misspelling of names that goes beyond typographical error. But anyone who knows the terrain will have a field day.