| Classification |
| Kingdom: Plantae
Division: Equisetophyta
Class: Equisetopsida
Order Type: Fern and Fern allies
Order: Equisetales
Family: Equisetaceae
Family Common Name: Horsetail Family
Genera: Equisetum |
Defining Features: Plant with
ribbed, jointed, hollow stems and whorled, basally connate scale leaves.
Defining Morphology: Group
consisting of one family, Equisetaceae, and one genus with 35 species.
Morphologically the shoot consists of distinct nodes and internodes. The
leaves are whorled and scale-like. In some species whorls of stems develop
at each node. The strobilus consists of a central axis on which spore-bearing
structures (sporangiophores) are arranged. These are umbrella-like with
sporangia attached on the underside around the central stalk. While Equisetum
is homosporous, fossil members of the phylum were heterosporous, and Equisetum
itself has a tendency to produce unisexual gametophytes. Spores are associated
with elators. The gametophytes are photosynthetic and fairly easy to grow
on a simple autotrophic medium. The Spenophyta is represented in the fossil
record from the Devonian; the order Equisitales from the upper Devonian.
Fossil members constitute a diverse group of both herbaceous and tree-like
forms. There are amazing similarities in stem anatomy between Equisetum
and arboreal forms from the Carboniferous. Shared anatomical features include
carinal canals associated with the primary xylem for each vascular bundle,
and a hollow pith. Additionaly, both Equisetum and extinct members of the
Equisetales have elators associated with their spores.
Distribution: Throughout the
world in moist to wet soils.
Economic Use: Stems are sold
as a tea in health food stores. Some species are poisonous to cattle.
Number of Genera Globally:
1
Number of Species Globally:
35
