The Seedless Vascular Plants:
Ferns and Their Relatives
Phylum Psilotophyta (Whisk Ferns)
Phylum Lycophyta (Club Mosses)
Phylum Equisetophyta (Horsetails)
Phylum Polypodiophyta (Ferns)
Fossil Forms
Phylum Psilotophyta
The Whisk Ferns
Loosely resemble small, green whisk
brooms
Structure and Form
Sporophytes consist almost entirely
of dichotomously forking aerial
stems
Have neither leaves nor roots
Enations spirally arranged
along stems
Phylum Lycophyta
Ground Pines, Spike Mosses, and
Quillworts
Collectively called club mosses
Two major genera
Lycopodium
Selaginella
Sporophytes have microphylls
Have true roots and stems
Phylum Lycophyta
Lycopodium - Ground Pines
Often grow on forest floors
Resemble little Christmas trees,
complete with cones
Stems are simple or branched
Develop from branching rhizomes
Reproduction
Phylum Lycophyta
Selaginella - Spike Mosses
Especially abundant in tropics
Branch more freely than ground
pines
Leaves have a ligule on upper
surface
Produce two different kinds of
spores and gametophytes
(heterospory)
Reproduction
Phylum Lycophyta
Isoetes - Quillworts
Most found in areas partially
submerged in water, and least part of
the year
Microphylls are arranged in a tight
spiral on a stubby stem
Ligules occur towards leaf base
Corms have vascular cambium
Reproduction
Phylum Equisetophyta
The Horsetails and Scouring Rushes
Structure and Form
About 25 species scattered
through all continents
Significant silica deposits
accumulate on the inner walls of
the stem’s epidermal cells
Branches, when present, are
normally in whorls at regular
intervals along the jointed stems
Phylum Equisetophyta
Both branched and unbranched species
have tiny microphylls in whorls at the
nodes
Leaves fused at their base forming a
collar
Stems are distinctly ribbed and have
obvious nodes and internodes
Pith breaks down at maturity leaving
a hollow central canal
Aerial stems develop from horizontal
rhizomes
Reproduction
Phylum Polypodiophyta
The Ferns
Structure and Forms
Approximately 11,000 known
species of ferns vary in size from
tiny floating forms less than 1 cm
to giant tropical tree ferns up to 25
m tall
Fern leaves are megaphylls that
are commonly referred to as
fronds
Typically divided into smaller
segments
Phylum Polypodiophyta
Human and Ecological Relevance
Extremely popular house plants
Cooked rhizomes serve as food
Folk Medicine
Fronds used in thatching
houses
Fossils
A fossil is generally defined as any
recognizable prehistoric organic
object preserved from past
geological ages
Conditions of formation almost
always include quick burial in an
accumulation of sediments
Hard parts more likely
preserved than soft parts
Fossils
Molds, Casts, Compressions, and
Imprints
After being buried in sediment, the
organic material may be slowly
washed away by water percolating
through the rock pores
If air space remains - Mold
If silica fills space - Cast
Compression takes place when
objects are buried by layers of
sediment and greatly compressed so
that only a thin outline is left
Questions?