Equisetum arvense “Common Horsetail” Equisetaceae
Lolo National Forest, Bitterroot Mountains, MT
May 10, 2015
Robert Niese
Horsetails were once abundant, diverse organisms, but today all surviving members of this ancient clade are restricted to a single genus with a worldwide distribution. This particular stalk is a fertile, strobilus-bearing stem. Their infertile counterparts look almost nothing alike!
Northwest Naturalist 