4/20/14 & 4/21/14: This week on "Fieldnotes:" "Horsetails," written by Kim Todd, read by Caroline Kurtz.
"Horsetails are like nothing else that still exists. They are the only surviving members of a single genus of a single family of the order Equisetales, which was in its heyday in the Carboniferous age, some 300 million years ago. At that time, while sharks were evolving in the water, and giant two-foot dragonflies zoomed overhead, relatives of the horsetails, called calamites, grew as tall as some of today's pines along the creek, towering 70 to 100 feet above the ground."