For the most part, symbolism is used in the play to highlight the tension between the old and the new, the traditional Africa and the modern Africa that is just coming into being.
For instance, we have the symbol of the postage stamps that Baroka promises to have printed with Sidi's photograph. The machine that Baroka says that he will use to print the stamps is modern, but his purpose is entirely traditional: he intends to play on Sidi's vanity and self-regard in the hope that she will marry him.
In this particular case, we have Baroka, very much a traditional African male, using the latest technological innovation as a means of getting what he wants. Sidi, as a modern woman, is understandably excited at the prospect of her photo appearing on potentially hundreds and thousands of stamps.
Yet in due course she will be drawn to Baroka, not so much because of his understanding of the latest technology but because he embodies all the old virtues that she believes will offer her financial and emotional security.
The symbol of the postage stamp, with its combination of the modern—Sidi's photo—and the traditional—Baroka's desire to make Sidi his wife—illustrates the constant tension that exists in a society in the process of modernization but still largely wedded to the old ways.