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The Green Machine
Understanding the Seedless Vascular Plants
21
To the Instructor
The seedless vascular plants include several plants with which students are familiar, such as ferns. These plants can serve
in “hands-on” experiments to introduce students to the seedless vascular plants. An understanding of this chapter is
necessary to understand plant evolution. This chapter can easily be modified to teach along with other chapters on plant
diversity. The instructor can pick and choose activities from these chapters to meet the needs of the students.
Topics for Discussion
77 At the beginning of this lab, review the objectives to the chapter. If this chapter is taught with other plant diversity
chapters, cover the objectives and material for the other chapters.
77 Discuss the classification and basic evolution of the seedless vascular plants.
77 Discuss the phyla of the plants included in this chapter, providing specific examples, natural history, uses, life history,
and anatomical information.
77 Discuss and bring in local specimens or photographs of the plants discussed in this chapter.
77 Discuss the environmental, industrial, and medical importance of the seedless vascular plants.
Total Estimated Completion Time: 2 hours, 30 minutes
1
Exercise
21.1
Phylum Lycophyta
Estimated Exercise 21.1 Completion Time: 40 minutes
Procedure 1
Macroanatomy of Lycopodium
Estimated Procedure 1 Completion Time: 10 minutes
Materials
❏❏ Dissecting microscope
❏❏ Living or preserved specimen of Lycopodium (Carolina Biological 156990)
❏❏ Colored pencils
Procedure 2
Microanatomy of Lycopodium
Estimated Procedure 2 Completion Time: 10 minutes
Materials
❏❏ Compound microscope
❏❏ Prepared slides of Lycopodium (Carolina Biological #’s 299818 and 299836)
❏❏ Colored pencils
Procedure 3
Macroanatomy of Selaginella
Estimated Procedure 3 Completion Time: 10 minutes
Materials
❏❏ Dissecting microscope
❏❏ Living or preserved specimen of Selaginella (Carolina Biological #157016)
❏❏ Colored pencils
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Procedure 4
Microanatomy of Selaginella
Estimated Procedure 4 Completion Time: 10 minutes
Materials
❏❏ Compound microscope
❏❏ Prepared slides of Selaginella (Carolina Biological #’s 299854 and 299878)
❏❏ Colored pencils
Check Your Understanding
1.1 Describe several uses of Lycopodium.
Medically, it has been used in homeopathic remedies including as an emetic, as a baby powder, and as a worming
agent. At Christmas, ground pines are used for decorations. Lycopodium spp. spores have been used in controlled
explosions, such as early photographic flashes. Lycopodium spp. have been used as a stabilizer in ice cream. The
spores have also been used as a fingerprint powder and in fireworks.
1.2 Where can one find Selaginella?
Selaginella spp. appear to creep along the ground with simple, scalelike leaves on branching stems from which
roots also arise. It is called resurrection plant because of its habit of curling into a tight ball and turning brown
when dry and opening out flat and turning green when water is again available.
1.3 Compare and contrast megaspores and microspores.
The megaspores are large spores that develop into a female gametophyte, which eventually produces egg cells.
The megaspores are fertilized by a sperm cell produced by the male gametophyte developing from the microspore.
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Exercise
21.2
Phylum Psilotophyta
Estimated Exercise 21.2 Completion Time: 20 minutes
Procedure 1
Macroanatomy of Psilotum
Estimated Procedure 1 Completion Time: 10 minutes
Materials
❏❏ Dissecting microscope or magnifying glass
❏❏ Living or preserved specimen of Psilotum if available (try university greenhouse)
❏❏ Colored pencils
Procedure 2
Microanatomy of Psilotum
Estimated Procedure 2 Completion Time: 10 minutes
Materials
❏❏ Compound microscope
❏❏ Prepared slides of Psilotum (Carolina Biological #’s 299176 and 299181)
❏❏ Colored pencils
Check Your Understanding
2.1 What is the common name for members of phylum Psilotophyta?
Phylum Psilotophyta is a rather obscure phylum of plants known as the whisk ferns.
2.2 Where is Psilotum usually found?
Psilotum spp. are commonly found in warm moist regions in the southern United States.
2.3 Describe several distinguishing features of phylum Psilotophyta.
The small plant has no leaves or roots and a dichotomously branching green stem with small scales that bears
bright yellow synangia on lateral branches. A synangium is formed from three fused sporangia on short lateral
branches. Psilotum spp. are homosporous. A horizontal rhizome gives rise to an aerial stem.
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Exercise
21.3
Phylum Sphenophyta
Estimated Exercise 21.3 Completion Time: 30 minutes
Procedure 1
Macroanatomy of Equisetum
Estimated Procedure 1 Completion Time: 10 minutes
Materials
❏❏ Dissecting microscope
❏❏ Living or preserved specimens of Equisetum, one branched and one unbranched (try local nursery)
❏❏ Colored pencils
Answers to Procedural Questions
2a Compare and contrast the external anatomy of the branched and unbranched forms of Equisetum.
Branched species of Equisetum spp. have whorl of branches imitating from each node, and other unbranched
­species have nodes without whorls.
2b
Describe the texture of the stem.
The stem is rough with parallel ridges.
Procedure 2
Microanatomy of Equisetum
Estimated Procedure 2 Completion Time: 10 minutes
Materials
❏❏ Compound microscope
❏❏ Prepared slides of Equisetum (Ward’s Science #’s 914814, 914818, and 914821)
❏❏ Colored pencils
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Procedure 3
Calamites Fossils
Estimated Procedure 3 Completion Time: 10 minutes
Materials
❏❏ Dissecting microscope or magnifying glass
❏❏ Fossil specimen of Calamites (Ward’s Science #535750)
❏❏ Colored pencils
Check Your Understanding
3.1 What is a whisk fern?
Whisk ferns are members of phylum Psilotophyta. The small plant has no leaves or roots and a dichotomously
branching green stem with small scales that bears bright yellow synangia on lateral branches.
3.2 What was Calamites?
Calamites spp. were giant members of the horsetail family that grew to heights of more than 20m during the
Carboniferous.
3.3 Describe several uses of horsetails.
Through the centuries, horsetails have been used as food and medicine. Today, however, the consumption of
horsetail is discouraged. Medically, ancient cultures used horsetail as diuretics; astringents; agents to discourage
lice, fleas, and mites; and a cure for diarrhea. Many Oriental gardens feature horsetails. Pioneers used horsetails
to scrub pots and sharpen knives.
3.4 Given the description of elaters provided on p. 327, describe their function.
Elaters are winglike structures found on the spores of horsetails. They serve to increase the distribution of the
spores.
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Exercise
21.4
Phylum Pterophyta
Estimated Exercise 21.4 Completion Time: 1 hour
Procedure 1
Macroanatomy of Ferns
Estimated Procedure 1 Completion Time: 20 minutes
Materials
❏❏ Dissecting microscope
❏❏ Living or preserved specimens of several species of ferns (local nursery, field, or other source)
❏❏ Scalpel
❏❏ Petri dishes
❏❏ Water
❏❏ Dropper
❏❏ Microscope slides and coverslips
❏❏ Acetone (Carolina Biological #841500)
❏❏ Rubbing alcohol
❏❏ Salt water
❏❏ Distilled water
❏❏ Gloves
❏❏ Colored pencils
Answers to Procedural Questions
5 Remove another sorus from the pinnae with a scalpel, and place it in a petri dish. Place one drop of acetone on the
sorus, and observe it with a dissecting microscope. What happened?
The sorus immediately popped open and released the spores.
6
Repeat Steps 3–5, using rubbing alcohol, salt water, and distilled water. What happened?
Running alcohol, salt water, and distilled water had no immediate effect on the sori.
Procedure 2
Microanatomy of Ferns
Estimated Procedure 2 Completion Time: 20 minutes
Materials
❏❏ Compound microscope
❏❏ Prepared microscope slides: pinnae (Ward’s Science #914901) and sori (Carolina Biological #299500) of a maidenhair fern, a fern
gametophyte, archegonia (Carolina Biological #299278) and antheridia (Carolina Biological #299248) of a gametophyte, a
transverse section through a stem of a fern, and a transverse section through a sporocarp of Marsilea
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Procedure 3
Bringing Polypodium Ferns Back to Life
Estimated Procedure 3 Completion Time: 20 minutes
Materials
❏❏ Dry Polypodium sp. (Carolina Biological #156396)
❏❏ Water
❏❏ Paper towels
❏❏ Plastic container
Answers to Procedural Questions
2 Make your observations.
Answers will vary.
Check Your Understanding
4.1 What is the function of sori?
The spores are produced in sporangia that appear as distinct brown spots on the underside of the frond, called
sori.
4.2 How does dried Polypodium sp. react to water?
The Polypodium sp. begins to regain its green color and becomes pliable.
4.3 Sketch and label a fern frond.
Sketches will vary, but make sure students label
pinna, stipe, rhizome, root, and fiddlehead.
Pinna
Stipe
Fiddlehead
Rhizome
Root
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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Chapter 21 Review
1
What are the general characteristics of seedless vascular plants?
The seedless vascular plants, as the name indicates, do not produce seeds but, instead, reproduce through
the ­production of spores. These plants feature a dominant sporophyte generation and a reduced gametophyte
generation.
2
Describe the characteristics of and provide examples of the following phyla: Lycophyta, Sphenophyta, Psilotophyta,
and Pterophyta.
Lycophyta—approximately 1,150 species of small plants known as ground pines, club mosses, quillworts, and spike
mosses make up phylum Lycophyta. In ground pines, an underground stem, the rhizoid, branches horizontally,
­producing aerial stems and underground roots. The surface of the aerial stem is covered by small, closely and
­spirally packed, scalelike leaves. Ground pines are homosporous. The reproductive sporangia, called sporophylls,
are located on the surface of leaves. A cone-shaped structure, a strobilus, sits at the tip and contains spores.
Sphenophyta—members of phylum Sphenophyta are known as horsetails or scouring rushes. Only one genus,
­Equisetum spp., represented by 25 species, remains today. Members of phylum Sphenophyta commonly live in wet
environments throughout the world. Modern species of Equisetum spp. are herbaceous and grow to about 1.5 m
in height. In horsetails, scalelike leaves are arranged in a whorl at the nodes. The tiny leaves are fused, forming a
collar that turns brown as the plant ages. The aerial stems of horsetails are deeply ribbed, and stomata occur in the
grooves between the ribs. Nodes and internodes are obvious in horsetails. The center of the stem, the pith, is hollow.
Rhizomes run horizontally across the ground and give rise to an aerial stem and roots. Horsetails can reproduce
asexually through fragmentation. Sexually, sporophyte horsetails produce strobili at the tip of the stem, composed
of scalelike sporangiophores. Beneath the sporangiophores, sporangia produce spores.
Psilotophyta—phylum Psilotophyta is a rather obscure phylum of plants known as the whisk ferns. Only two genera
survive today—Psilotum sp. and Tmesipteris sp. Psilotum sp. is commonly found in the southern United States. The
small plant has no leaves or roots and a dichotomously branching green stem with small scales that bears bright
yellow synangia on lateral branches. In Psilotum sp., a horizontal rhizome gives rise to an aerial stem.
Pterophyta—ferns placed in phylum Pterophyta (Polypodiophyta) are the most abundant group of seedless vascular
plants. The sporophyte stage is dominant in ferns. The leaves of ferns, known as fronds, arise from rhizomes.
­Immature fronds develop from the tip of a rhizome and appear as a tightly coiled and rolled-up structure called
a fiddlehead. Compound frond ferns possess ornate leaflets, or pinnae. Simple frond ferns have leathery, broad,
unbranched, strap-like fronds. The pinnae are attached to a midrib, sometimes
called a rachis. A petiole, or stalk, attaches the pinnae to the rhizome. Other ferns
have leathery, broad, unbranched, strap-like fronds. Branching roots also arise from
Strobilus
the rhizomes. Most fern species are homosporous. The spores are produced in
­sporangia, appearing as distinct brown spots on the underside of the frond, called
sori. Example ferns include the resurrection fern, the royal fern, and the water fern
(Polypodium polypoidioides).
3
Sketch and label Equisetum sp.
Sketches will vary, but make sure students include mature sporophyte (2n),
­strobilus, node, ribbed stem, leaf sheath, and rhizome.
4
Mature
sporophyte
(2n)
Distinguish between the sporophyte and the gametophyte generation
in seedless vascular plants.
These seedless vascular plants feature a dominant sporophyte generation
and a reduced gametophyte generation.
Node
Ribbed
stem
Leaf
sheath
Rhizome
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5
What are some commercial and medical uses of seedless vascular plants?
Seedless vascular plants, such as ferns, are used in medicine and as ornamentals. Horsetail can be used as
­medicine and to sharpen knives. Lycopodium spp. are used as decoration and, at one time, in camera flashes.
6
Compare and contrast Lycopodium sp. and Selaginella sp.
Selaginella spp. appear to creep along the ground with simple, scalelike leaves on branching stems from which
roots arise. The leaves of Selaginella spp. have a distinct ligule, or tongue, on their upper surface and generally
appear larger than Lycopodium spp. In Lycopodium spp., an underground stem branches horizontally across the
surface, producing aerial stems and underground roots. The surface of the aerial stem is covered by small, closely
and spirally packed, scalelike leaves.
7
How did the pioneers use horsetail?
Pioneers used horsetail to scrub pots and sharpen knives.
8
Portion of leaf
showing sori
Trace the life cycle of a typical fern.
Sketches will vary.
Leaf vein
Pinna
(frond)
Fiddlehead
Sporangium
Meiosis
Root
Mature sporophyte (2n)
Meiospores (n)
Young sporophyte
Gametophyte
Young
gametophyte (n)
Young sporophyte (2n)
growing from gametophyte
Rhizoids
Archegonium
Egg (n)
Mature
gametophyte
Embryo (2n)
Zygote
Fertilization
Sperm (n)
9
Antheridium
What is the significance of the vast fern forests of the Carboniferous?
Many of the coal deposits of today were formed from Carboniferous forests.
10 What is the function of a sporangium?
The function of sporangia is to produce haploid spores through meiosis.
Chapter 21 | The Green Machine: Understanding the Seedless Vascular Plants
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