Lycophyta

Plants in the Lycophyta have Erect Stems as well as Stolons and Rhizomes. They are relatively large compared to Hepatophyta, and Bryophyta but they rarely exceed a meter in height. They can be epiphytes and their pendant stems can be more than a meter in length.

Branching is Isotomous Dichotomous for both Roots & Shoots. Isotomous means that each branch develops equally.

The Apical Meristem can have several "Initials" rather than a solitary Apical Cell. This is somewhere between an Apical Cell and the Multicellular Apices of flowering plants.

The production of Leaves from the Shoot Apical Meristem is similar to that of a flowering plant

These plants are most abundant in the tropics but a few can survive cold, dry environments. This includes the "Ressurection Plant". This plant curls up like a ball when it is dry, and rolls around arid habitats until it finds a source of water. It then, unfurls and turns green!

A composite Lycopodium	A species growing in the Arctic/Alpine zone near Jasper Canada. This plant is approx. 10 cm in length.
*Vertical Lycopodium* with Isotomous Branching. This plant is about 15-20 cm tall.**	*A Pendant Epiphytic Lycopodium* from Puerto Rico. note the Isotomous Branching. This plant is over 1m in length.**
*A local Lycopodium* showing Isotomous Branching and well developed Microphylls.**	Lycopodium lucidulum: Note the Vertical Stem. The Roots are adventitous and originate in the stem. They branch Isotomously.
Shoot tip of L. lucidulum: Microphylls Galore!!!!	Roots from the image above: Note the Isotomous Branching.
*Cross section of a Lycopodium* Microphyll: Note the Uniform (unspecialized) Mesophyll and the Cuticle. Stomata are visible on the upper side of the leaf.**
The species to the right grows locally on disturbed sites and could be a candidate for soil stabilization research. It is a complex plant which has horizontal Stolons which have Isotomous Branching. These produce the Roots which anchor the plant to the substrate. The Stolons also produce Aerial Shoots which have Anisotomous (Unequal) branching. When dichotomous branches develop unequally (on=short & 1=long) the branching is called Anisotomous. The upright stems are about 1 m in height.
Simple Stele (Haplostele) from a Lycopod Root. Note the central core of Xylem surrounded by Phloem and an Endodermis.
Cross section of a Lycopodium Rhizome: A Rhizome is a horizontal subterranean stem. The Stele is more complex than that of the Root above. Bands of Xylem are surrounded by Phloem. The Phloem is unstained in this image. Note the extensive Sclerenchyma in the Ground Tissue.
*Cross section of L. lucidulum* Aerial Stem: The Cortex contains mostly Parenchyma which has a pink color. The Xylem (stained blue) is prominent in the Stele.**
Stele from a Lycopodium Stem: The Xylem resembles sheets or flaps. Each arm is surrounded by Phloem and an Endodermis. This is called a Plectostele (Plecto = Plate). This is more complex that the stele in Psilotum. The Leaf Traces are small Vascular Bundles which diverge from the central Stele and connect with the vein in the leaf. This produces a fully integrated vascular system that includes the three major vegetative organs and reproductive leaves.

While extant Lycopods are small plants with little ecological significance. Forests of tree-sized lycopods once dominated certain habitats. The most famous of these is Lepidodendron which reached heights up to 30 meters. They had secondary growth. The stems were coated with leaf bases and there appeared to be little internodal elongation. The latter implies that the trees had slow growth which may partly account for their extinction.

The next major step in evolution was the development of a complex leaf called a Megaphyll.