Symbols

the woman
willy's way of dealing with his material problems
linda mending stockings are reminder to willy of his unfaithfulness

jungle
the immoral rise to success which willy idolises

whistling
willy portrays whistling as rudimentary
willy says bernard does not whistle in elevators
bernard whistles in the reception of charley's office

seeds
Linda: [laughing]: That’d be wonderful. But not enough sun gets back there. Nothing’ll grow any more."
Willy: "I’ve got to get some seeds, right away. Nothing’s planted. I don’t have a thing in the ground."
happy and biff enter with roses after dinner at the restaurant with willy
the seeds represent the american dream