The Seedless Vascular Plants: Ferns and Their Relatives
Psilotophyta (Whisk Ferns)
Lycophyta (club mosses)
Four phyla -characterized by the presence of vascular tissue but still have spores not seeds and
need water to reproduce. They have independent gametophyte and sporophyte and show
alternation of generations.
Age of Ferns
Ferns were the dominant vegetation 350 million years ago. Shown below is a drawing of the
prehistoric habitat. Most of the trees are giant club mosses. The frondlike leaves in the
foreground are seed ferns. On the right is a giant horsetail.
The Whisk Ferns Loosely resemble small, green
whisk brooms. Believed to be present since
Silurian period ~ 400 million years ago
Sporophytes consist almost entirely of
dichotomously forking aerial stems.
Have neither leaves nor roots.
Enations –tiny green, leaf-like, veinless
photosynthetic flap tissues -spirally arranged
Life Cycle: Shows alternation of
Phylum 1. Lycopodium-Ground Pines approx. 50 species
Often grow on forest floors. Resemble little Christmas trees, Resemble little Christmas trees,
complete with cones. Stems are simple or branched. Develop from branching rhizomes with
roots. Leaves are small.
Reproduction Diploid sporophyte –dominant. Spores are produced in spore bearing leaves
called sporophylls. Sporophylls are arranged in a conical shaped structures at the terminal end
of structures at the terminal end of a branch called strobilus. Sporangia are produced in the axils
of sporophylls as kidney shaped structures. Sporocytes undergo meiosis to produce haploid
spores –germinate into gametophyte.
Phylum 2. Lycophyta - Selaginella-Spike Mosses –about 750 species.
Especially abundant in tropics.
Branch more freely than ground pines. Leaves have a ligule (tongue-like append.) on upper
surface. Produce two different kinds of spores –microspores and megaspores (heterospory) germinating into two separate gametophytes
Megasporophylls–produce megasporangium–in which 4 mega spores are produced