Vascular Seedless Plants Whisk Ferns, Club Mosses and Horsetails

Whisk Ferns Whisk ferns are widespread, rootless and green- stemmed. –Instead of leaves, they possess enations along the angular stem axis. They contain a 3-lobed spore-producing structure called a synangium.

Whisk Ferns cont. Whisk ferns are regularly branched, with scale like outgrowths that resemble small leaves. –They are anchored by a rhizome, or root-like stem, which absorbs nutrients by means of filaments called rhizoids. Whisk ferns are some of only a few surviving members of an ancient group of vascular plants.

Life Cycle of Whisk Ferns There are two phases in the life cycle of a whisk fern. The large asexual plants (sporophytes) produce spores that develop into small, sexual plants (gametophytes). –Eggs and sperm are produced in special structures on their surfaces. They then reproduce sexually to create the next plant.

Where can they be found? Whisk ferns thrive in the warm weather of the tropics and subtropics, so there are no species of them in our area.

Club Mosses Club mosses are flowerless and seedless plants that were dominant during the coal age ( million years ago) and many were shrubs or large trees. –Many of those species have since died out. About genera and 400 species are still around.

Structure Club mosses are structurally similar to the earliest vascular plants. They contain small, scale-like leaves, spores borne in sporangia at the base of the leaves, and branching stems.

Life Cycle of Club Mosses The spores germinate to produce bisexual gametophytes that are green and photosynthetic. –The maturation of a gametophyte may require 6 to 15 years. Biflagellated sperm are produced in an antheridium (male reproductive organ) and an egg is produced in a flask-shaped archegonium. –Water is required for the sperm to swim to another gametophyte and down the neck of an archegonium to reach the egg at the bottom. The young sporophyte produced after fertilization may remain attached for many years, and in some species the gametophyte may continue to grow and produce a succession of young sporophytes.

Species in Minnesota There are about 12 species in Minnesota. They are mainly the smaller species. –They are all terrestrial, and grow in the pine woods. They are also known as ground pines.

More about club mosses Many club mosses produce masses of sulfur-colored spores that are highly inflammable and were once used as a constituent of flash powder in early photography and in fireworks. They were also formerly used by pharmacists to coat pills.

Horsetails Horsetails are very nearly allied to ferns. Their stems spring from a creeping rhizome, which produces roots. –Both barren and fertile stems are produced. They are erect, jointed, brittle and grooved. They are hollow everywhere except at the joints, and have air-cells in their walls under the grooves.

Horsetails cont. They contain no leaves, the joints terminate in toothed sheathes, with the teeth corresponding with the ridges and representing leaves. The branches arise from the sheath bases and are solid. –Usually, the fruiting stem is unbranched and withers in spring. They contain microscopic spores, attached to elastic threads, which are coiled around the spore when moist and uncoiled when dry.

Life Cycle of Horsetails Sporangia are clustered in cones (strobili) at the tips of vegetative shoots. –They hang in groups of 5 to 10 from umbrella-like sporangiophores that compose the strobili. Each spore is wrapped in four thickened bands called elaters. As the elaters dry, they twist and turn giving buoyancy to the spores. The spores germinate and produce gametophytes, which anchor with rhizoids to a moist surface rich in nutrients.

Horsetails life cycle cont. Multiflagellate sperm swim in water to the archegonium, and the egg at the base is fertilized. The zygote forms an embryo in the archegonium and the young sporophyte is nourished by the gametophyte to which it is attached until the organs are sufficiently developed to sustain the sporophyte independently.

Species There are about 30 species of horsetail in the world. A few of them are common right here in Minnesota, such as the scouring rush horsetail, which is commonly found in ditches alongside roads. Another is the forest horsetail, which is commonly found in northern Minnesota.

Pictures of Horsetails