(C) Sphenophyta - "Horsetails"

    Arborescent and understory sphenophytes were common associates of the tree lycophytes in the Carboniferous forests. The only remnant of this once prominent group is a single herbaceous genus, Equisetum, with 25-30 species. It is still widely distributed, however, and in some moist areas it can be quite abundant. Several species are common in California.

    The sporophyte of Equisetum has an underground rhizome from which arise erect vegetative and reproductive shoots. The stem is a system of nodes (hollow) and internodes (solid). Observe the whorls small leaves at the nodes of the shoots, and the terminal strobili on the reproductive shoots.  Whorled branches may also be present at the nodes. The walls of the epidermal cells contain large amounts of silica, which made the stems useful to early settlers in North America for scouring cookware, and another name for these plants is "scouring rushes."

   Examine the sporophytes available. Note the branching pattern, and the way leaves are attached. 

Equisetum giganteum	Whorled branches at nodes of E. giganteum.	Node of Equisetum, showing whorled leaves.	Strobilus of Equisetum