Are Heirloom Varieties the Only Ones from Which Seeds Can Be Saved to Produce Another Plant?

http://www.motherearthnews.com/organic-gardening/saving-seeds-with-heirloom-varieties.aspx

Are heirloom varieties the only ones from which seeds can be saved to produce another plant? I've heard that the hybrids will not grow from saved seed. 

Barbara Dodds
Blythewood, South Carolina

Seeds saved from a hybrid variety can be saved and replanted, but they won’t “grow true” to the original parent plant. 

Hybrids are a cross between two purebred lines. For example, a plant breeder might cross one variety of squash having good color with another having good taste with the goal of creating a second generation plant having both desirable traits. Seeds saved from a first generation hybrid (F1) and replanted will produce a second generation hybrid (F2) which lacks the vigor of its parent and may show some of the undesirable characteristics of the two pure varieties crossed to produce that parent. 

Heirloom or open-pollinated seeds are the only ones that can be saved and replanted to reproduce a copy of the original plant. 

 Roger Doiron, contributing editor