Neal Grundy, Ivy PressThe seed of the pong-pong tree is among the examples featured in “The Book of Seeds.” By Erin Blakemore, Special to The Washington Post Chances are, you’ve never given seeds much thought. Maybe you strew them around your garden each spring. Maybe you pour them into your salad. But seeds are more than snacks – they’re little repositories of the genetic information that makes the plant world tick.