Lab #7 - Seedless Vascular Plants
Lab #7 Seedless Vascular Plants
Introduction
In today’s lab, we will study seedless vascular plants. This plant group evolved by the late Devonian period and
was the prominent group during the Carboniferous period of the Paleozoic era. They formed the first forests
about 385 million years ago. These forests are the main source of fossil fuels we use today. Critical innovations
that lead to the success of seedless vascular plants were the vascular tissue and wind-blown spores. The
vascular tissue is made up of xylem (which conducts water) and phloem (which conducts organic material).
Unlike seedless non-vascular plants, seedless vascular plants have true leaves (meaning leaves with veins),
stems and roots. Seedless vascular plants include two phyla: Phylum Lycophyta (club mosses) and phylum
Pteridophyta (Ferns).
Seedless vascular plants exhibit alternation of generations with a dominant sporophyte plant alternating with
a haploid gametophyte plant. The sporophyte is well adapted to life on land and bears the sporangia (spore
bearing structures). The cells in the sporangia undergo meiosis to form haploid spores. In most seedless
vascular plants, sporangia are borne adjacent to specialized leaves called the sporophylls. The sporophylls
with sporangia sometimes aggregate into structures called strobili.
The strobili can bear spores of the same kind (homosporous) or of different kinds (heterosporous). The spores
germinate to form the haploid gametophyte. In seedless vascular plants, the gametophyte is small but
photosynthetic; it bears gametangia – antheridia and archegonia that produce sperm and eggs, respectively.
During fertilization, the sperm swim to the egg resulting in a diploid zygote. The zygote then develops into a
young sporophytic plant which eventually grows Your
into a text here 1and independent sporophyte.
dominant
Phylum Lycophyta (club mosses)
In today’s lab you will observe two Lycophytes - Lycopodium and Selaginella.
Lycopodium is a small upright plant with simple leaves bearing a single mid vein. These leaves are called
microphylls. The plant body, which is a diploid sporophyte, bears spores in sporangia. In Lycophytes the
sporangia are arranged in specialized structures called strobili which are club shaped (hence the common
name club mosses). The sporangia of Lycopodium are homosporous (spores of the same kind)
1
, Lab #7 - Seedless Vascular Plants
Selaginella is a small, creeping lycophyte. The plant body is a sporophyte. It also bears microphylls with
sporangia aggregated in strobili. The sporangia of Selaginella are heterosporous. Selaginella is commonly
called spike moss.
Phylum Pteridophyta (Ferns)
Pteridophytes are also called true ferns. They are quiet diverse and range widely in size. All ferns are
characterized by megaphylls -leaves with highly branched veins. The dominant sporophyte is photosynthetic.
The examples of Pteridophytes you will observe in today’s lab are
Psilotum (commonly called whisk fern)
Equisetum (commonly called horsetails)
Pteris (the Common Fern)
Pre-Lab Questions
Whisk fern – Psilotum Horse tail - Equisetum Fern - Pteris
nudumnudum
yes
1. Do seedless vascular plants exhibit alternation of generations? ______________________
2. Is dominant plant body of seedless vascular plants n (haploid) or 2n (diploid)?ynpiploid
__________
sporophyte
3. Is it a sporophyte or gametophyte? ____________________________________________
4. List two critical innovations that lead to the success of seedless vascular plants:
a. vascular tissue
Hyrum
___________________________________________________________________ )
and phloem
wind blown spores
b. ___________________________________________________________________
spores
5. Do Lycophytes and Pteridophytes reproduce by spores or seeds? _____________________
6. Name the two major phyla of seedless vascular plants:
lycophyta
a. ___________________________________________________________________
Pteridophyte
b. ___________________________________________________________________
2
Lab #7 Seedless Vascular Plants
Introduction
In today’s lab, we will study seedless vascular plants. This plant group evolved by the late Devonian period and
was the prominent group during the Carboniferous period of the Paleozoic era. They formed the first forests
about 385 million years ago. These forests are the main source of fossil fuels we use today. Critical innovations
that lead to the success of seedless vascular plants were the vascular tissue and wind-blown spores. The
vascular tissue is made up of xylem (which conducts water) and phloem (which conducts organic material).
Unlike seedless non-vascular plants, seedless vascular plants have true leaves (meaning leaves with veins),
stems and roots. Seedless vascular plants include two phyla: Phylum Lycophyta (club mosses) and phylum
Pteridophyta (Ferns).
Seedless vascular plants exhibit alternation of generations with a dominant sporophyte plant alternating with
a haploid gametophyte plant. The sporophyte is well adapted to life on land and bears the sporangia (spore
bearing structures). The cells in the sporangia undergo meiosis to form haploid spores. In most seedless
vascular plants, sporangia are borne adjacent to specialized leaves called the sporophylls. The sporophylls
with sporangia sometimes aggregate into structures called strobili.
The strobili can bear spores of the same kind (homosporous) or of different kinds (heterosporous). The spores
germinate to form the haploid gametophyte. In seedless vascular plants, the gametophyte is small but
photosynthetic; it bears gametangia – antheridia and archegonia that produce sperm and eggs, respectively.
During fertilization, the sperm swim to the egg resulting in a diploid zygote. The zygote then develops into a
young sporophytic plant which eventually grows Your
into a text here 1and independent sporophyte.
dominant
Phylum Lycophyta (club mosses)
In today’s lab you will observe two Lycophytes - Lycopodium and Selaginella.
Lycopodium is a small upright plant with simple leaves bearing a single mid vein. These leaves are called
microphylls. The plant body, which is a diploid sporophyte, bears spores in sporangia. In Lycophytes the
sporangia are arranged in specialized structures called strobili which are club shaped (hence the common
name club mosses). The sporangia of Lycopodium are homosporous (spores of the same kind)
1
, Lab #7 - Seedless Vascular Plants
Selaginella is a small, creeping lycophyte. The plant body is a sporophyte. It also bears microphylls with
sporangia aggregated in strobili. The sporangia of Selaginella are heterosporous. Selaginella is commonly
called spike moss.
Phylum Pteridophyta (Ferns)
Pteridophytes are also called true ferns. They are quiet diverse and range widely in size. All ferns are
characterized by megaphylls -leaves with highly branched veins. The dominant sporophyte is photosynthetic.
The examples of Pteridophytes you will observe in today’s lab are
Psilotum (commonly called whisk fern)
Equisetum (commonly called horsetails)
Pteris (the Common Fern)
Pre-Lab Questions
Whisk fern – Psilotum Horse tail - Equisetum Fern - Pteris
nudumnudum
yes
1. Do seedless vascular plants exhibit alternation of generations? ______________________
2. Is dominant plant body of seedless vascular plants n (haploid) or 2n (diploid)?ynpiploid
__________
sporophyte
3. Is it a sporophyte or gametophyte? ____________________________________________
4. List two critical innovations that lead to the success of seedless vascular plants:
a. vascular tissue
Hyrum
___________________________________________________________________ )
and phloem
wind blown spores
b. ___________________________________________________________________
spores
5. Do Lycophytes and Pteridophytes reproduce by spores or seeds? _____________________
6. Name the two major phyla of seedless vascular plants:
lycophyta
a. ___________________________________________________________________
Pteridophyte
b. ___________________________________________________________________
2
