PTERIDOPHYTES

Ferns and Fern Allies

The Pteridophytes (seedless vascular plants) consist of 4 Divisions circa 1993 (Flora of NA, V. 1)

due to their similarities (discussed below) in anatomy and morphology and their differences from

higher seed plants*.

1- Lycopodiophyta (Club-Mosses)

2- Psilotophyta (Whisk Ferns)

3- Equisetophyta (Horsetails)

4- Polypodiophyta (True Ferns)

Reproduction is by spores (also by vegetative or asexual means) - no true flowers, fruits or

seeds are present. They exhibit a life cycle of alternation of generations (sporophyte and

gametophyte). The sporophyte generation is the larger phase that we commonly see in the field and

produces haploid spores by meiosis. These spores disseminate mostly by wind (sometimes water),

produce a Prothallus (gametophyte generation), a very small, free-living or independent phase, that

produces both sperm (from antheridia) and eggs (from archegonia) – gametes or sex cells. The

sperm swims to the egg on its own prothallus or on another (water must be present in most cases)

and fertilization results with the production of the diploid generation from which a new sporophyte

generation is produced.

World-wide there are about 25 families, 255+

genera, and perhaps 10,000+ species. In North

America there are about 77 genera and 440+

species (Flora of North America, V.2). – see

next slide for more information.

*Botanists today, due to DNA studies and many additional examples, believe that the Lycophytes branched

early (forming a distinct Clade or branch of a phylogenetic tree) and the Pteridophytes form another later

distinct Clade (or branch) that is closer to the seed plants (a revised classification is below).

1- Phylum Pterophyta – ferns, horsetails, and whisk ferns

2- Phylum Lycophyta – club mosses, spike mosses, and quillworts

PTERIDOPHYTES World World N.A. N.A. MO MO Genera Species Genera Species Genera Species

PSILOTOPHYTA (WHISK FERNS)Psilotaceae (Wisk-fern Family) 3 4-8 1 1 - -

LYCOPODIOPHYTA (CLUB-MOSSES)Lycopodiaceae (Club-moss Family) 10-15 350-400 7 27 2 5Selaginellaceae (Spike-moss Family) 1 700+ 1 38 1 3Isoetaceae (Quillwort Family) 1 150 1 24 1 3

EQUISETOPHYTA (HORSETAILS)Equisetacae (Horsetail Family) 1 15 1 11 1 3

POLYPODIOPHYTA (FERNS)Ophioglossaceae (Adder’s Tongue family) 5 70-80 3 38 2 7Osmundaceae (Royal Fern Family) 3 16-36 1 3-4 1 3Gleicheniaceae (Forking Fern Family) 4 140 1 1 - -Schizaeaceae (Curly Grass Family) 2-3 30 2 2 - -Lygodiaceae (Climbing Ferns) 1 40 1 3 - -Anemiaceae (Family) 2 119 1 3 - -Parkeriaceae (Water Fern Family) 1 3-4 1 3 - -Pteridaceae (Maidenhair Fern Family) 40 1,000 13 90 4 9-11Vittariaceae (Shoestring Fern Family) 10 100 1 3 - -Hymenophyllaceae (Filmy Fern Family) 6 650 2 11 - -Dennstaedtiaceae (Family) 20 400 4 6 2 2Thelypteridaceae (Marsh Fern Family) 1-30 900 3 25 2 2 Blechnaceae (Chain Fern Family) 10 250 2 6 1 1 Aspleniaceae (Spleenwort Family) 1 700 1 28+ 1 8Dryopteridaceae (Wood Fern Family) 60 3,000 18 79 9 17 Grammitidaceae (Family) 10+ 500+ 1 1 - -Polypodiaceae (Polypody Family) 40 500 7 25 1 2 Marsileaceae (Water-clover Family) 3 50 2 7 2 2 Salviniaceae (Floating Fern Family) 1 10 1 1 - -Azollaceae (Azolla Family) 1 7 1 3 - -

PTERIDOPHYTES -

The Ferns and their

Allies (number of

genera and species)

for the World, North

America, and the state

of Missouri.

Data from The Flora of North

America (Vol. 2, 1993) and Flora

of Missouri (Vol. 1, 1999)

Anatomy and Morphology of the Ferns and “so-called” Allies

(revised classification)

1- Phylum Pterophyta (ferns, horsetails, and whisk ferns)

Ferns – slide 4 (Anatomy present)

Horsetails – slide 34 (Anatomy present)

Whisk Ferns – slide 44 (Introduction only)

2- Phylum Lycophyta (club mosses, spike mosses, and quillworts)

Club Mosses – slide 45 (Introduction only)

Spike Mosses – slide 50 (Introduction only)

Quillworts – slide 51 (Introduction only)

Phylum Pterophyta – The Ferns (20+ Families) – Definition [V. Max Brown]

To define a Fern is not so easy due to their great diversity with 10 orders, 20+ families and many

genera. It turns out that Horsetails are actually ferns (DNA studies) and are now included within their

evolutionary tree (order Equisetales).

Fern characteristics (fern families):

1 – Their DNA sequences form a natural group even if they sometimes look quite different.

2 – Most ferns have “fiddleheads”, the leaves unfurl spirally (tip rolled into center) but a few uncoil

lengthwise. Most leaves on the larger sporophyte phase are compound (with leaflets) and most

arise from a horizontal stem.

3 – If pneumatophores are present (air breathing structures on the petiole) it must be a fern (A

Natural History of Ferns by Robbin Moran, 2004).

4 – Ferns are Seedless Vascular Plants with Megaphylls (branched vascular systems)

5 – Most ferns are Homosporous (with one type of spore) but a few are Heterosporous. Sporangia

are borne on the lower surface of the leaf.

Fern Morphology – Typical Fern (sporophyte phase) [V. Max Brown]

Stipe - sometimes termed the Stem, supporting

Stalk or Petiole of the Frond

Frond – Stipe and Blade taken together

Blade – leaf portion of Frond, the

Axis (stem portion or midrib) of the

blade is termed the Rachis

Rhizome – “rootstalk” of fern (this is

actually stem-type of tissue, not a true

root) – hidden by moss in upper photo

Adventious Roots – true roots growing from the

underground stem material (the Rhizomes) –

termed adventious because roots do not normally

grow from stems

Resurrection Fern [Gray’s Polypody]

Pleopeltis polypodioides (L.)

Andrews & Windham subsp.

michauxiana (Weath.) Andrews &

Windham leopeltis

Ferns may be terrestrial (rooted on soil or on or in

cracks of rocks), epiphytic (rooted to branches or

trunks of trees, high or low), and even a few are

aquatic.

Circinate Vernation – coiled

from the tip (meristem at tip),

and rolled down and in. Growth

by unfolding is termed

acropetal growth. These young

unfurling fronds are termed

Fiddleheads or Crosiers.

Many but not all ferns develop

in this fashion – a few have

Intercalary meristems (growth

at nodes or stem areas) and

unfold length-wise. This is

termed Conduplicate

Vernation (not shown).

Basic Fern Morphology – Leaf Development[V. Max Brown]

Vernation (leaf development)

Fern Morphology – The Blade [V. Max Brown] The fern Blade may be Simple (margins may be lobed, etc.) but

more often blades are Compound (divided 1 or more times)

Simple blade – may

be lobed, toothed, etc.

but the depth of these

decorations are much

less than ½ distance to

midrib.

Compound blade – blade is divided (once divided or cut) but

not all the way to the midrib leaving a winged rachis. This is

termed a Pinnatifid Blade. The individual lobes of the Blade

are technically termed Segments (lobes not stalked or cut to

midrib) but are often still called Pinna (Pinnae) (see next

slide for explanation).

Segment

Winged Rachis – not cut to midrib

Any difference in

orientation of Pinnae

(segments) may be

important in ID –

lower pair of leaves

here deflexed

Overall blade shape is

important for ID – is it

deltoid, lanceolate,

etc.; does it taper at

both ends or not, etc.

Simple Pinnatifid (compound)

Compound blade – blade is divided to the

rachis or midrib. This is termed Pinnate

(also once divided or cut). Individual

segments are true Pinna (Pinnae).

Pinnate (compound)

Fern Morphology – The Blade [V. Max Brown]

Pinnatisect (compound)

Compound blade – blade is divided to the

rachis or midrib only at the sinus between

lobes.

On the left the lobes are divided to

the rachis but only at the Sinus.

These lobes then would be

Segments and not true Pinna. A

Pinna (strict definition) has the lobe

narrowing to the rachis on both sides

or look stalked (see right, a true

Pinnate blade with Pinna). Some

authors do not use Pinnatisect.

Note – most species do not show a

raised dot on the upper surface of

the leaf from the Sori (fruiting

structures) below.

*Warning – the term Segment is often not used in a strict sense

Fern Morphology – The Blade [V. Max Brown]

Pinnate-Pinnatifid (compound) Bipinnate (compound)

Compound blade – blade is twice divided to

the rachis or midrib. This is termed

Bipinnate (also twice divided or cut).

Individual segments are also Pinnules.

Pinnae

1 Pinnule of

the Pinnae

Compound blade – blade is once divided to

the rachis or midrib and then partially cut. This

is termed Pinnate-Pinnatifid (Pinnules

partially cut)

Compound blade - If neither first or second

divisions reach the axis it would be Biipinatifid

(no example shown).

Pinnae and Pinnules are usually Alternate to

Sub-Opposite, sometimes truly opposite.

Fern Morphology – The Blade [V. Max Brown]

Compound blade – blade is twice divided to

the rachis or midrib and then partially cut.

This is termed Bipinnate-Pinnatifid

(Pinnules partially cut)

Compound blade - If neither first, second or

third divisions reach the axis it would be

Tripinatifid (no example shown).

Compound blade – blade is cut three times to

midrib. This is termed Tripinnate. Last segments

are still termed Pinnules.

Much divided fronds are sometimes simply referred

to as Decompound

Tripinnate (compound)

Bipinnate-Pinnatifid (compound)

The example at left is

pinnate near the tip and

bipinnate near the base.

It is not unusual for a

species to be described

such as this; pinnate to

pinnate-pinnatifid or

rarely bipinnate.

Fern Morphology – The Blade [V. Max Brown]

3+ Pinnate (Compound)

In this case the Blade (rachis) is

branched into 3 segments (1st division),

and so forth – stem divisions are

usually in a horizontal plane

Upper stipe and rachis divides into 2 main divisions forming

a horizontal fan-shaped or Flabellate Blade. The blade has

several (3-9) secondary rachises each with pinnate

components in which the segments have incised margins.

Two separate ferns are present in photo above

Sometimes it gets difficult to describe with branching of the stipe and rachis

Secondary

rachis

Fern Morphology – Leaflet FeaturesV. Max Brown]

Margins smooth (entire or continuous),

apex rounded

Narrow to wide trowel-shaped

to lanceolate with Dentate

teeth (pointed outward) to

Lacerate (irregular) teethLeaflet long-deltoid with truncate base,

margin finely Serrate (teeth directed forward)

Leaflets with coarse Serrate teeth

(Serrate - teeth directed forward)

Leaflet Auriculate (eared) at base,

serrate with teeth tipped with bristles,

segments Coriaceous (Leathery)

Leaflet shape almost ovate

(bead-like) with long hairs,

margins rolled under

(Revolute)

Tipped with a Bristle

Fern Morphology – Leaflet Features V. Max Brown]

Acroscopic (ear facing tip or apex

of frond) Auriculate (eared) – so

Acroscopic Auriculate.

Both Acroscopic (facing tip

and Basiscopic (facing base)

Auriculate (eared)

Margins Erose (irregularly toothed),

eared (Acroscopic Auriculate)

Fleshy and Glaucous

(whitish coating)

Some leaves have one “ear” oriented either up or down or,

some leaves have 2 symmetrical basal ears.

Simple Areoles (defined areas) in a

reticulated (net-like) vein pattern without

included elements in the Areole areas

(sometimes blind or free veinlets are found

within the Areoles). These anastomosing

patterns may only be present in parts of a

segment.

Fern Morphology – Leaflet VenationV. Max Brown]

Forked veins from midrib, fairly

simple with one branch (a simple

vein does not fork)

Forked veins from midrib, with multiple forking sometimes ending

at teeth or between teeth

Forked veins without a well-defined

midrib (close to being Dichotomous)

Free Veins – many pinnately branched from a rachis

Reticulated Veins

Dichotomous Veins

Dichotomous veins are found in a few ferns

(no midrib). The veins fork from the base

to the tip of the segment with nearly equal

angles at each fork.

Fern Morphology – Grooved AxesV. Max Brown]

The axes of the frond is sometimes grooved on the adaxial (upper) surface but not on

the abaxial side. These grooves are often but not necessarily aligned with different

order axes.

Not grooved

on abaxial side

Secondary rachis not

grooved on adaxial side

of axis

Fern Morphology – Rhizomes and RootsV. Max Brown]

The stems of ferns are mostly true Rhizomes

(stems that run horizontally either along the top

of the ground or just beneath the surface of the

ground).

Rhizome (on rock surface),

note branching

Rhizome

Rhizome

Stipe (part of leaf or fronds)

Stipe

True Rootlets

True Rootlets

The roots are adventurous (from a stem).

They are mostly wiry but can be somewhat

fleshy. Abundant root hairs may be present

near the tips of roots.

Rhizomes may branch or not (branching may

be irregular or somewhat symmetrical). They

are often protected by hairs, scales, and

bristles.

Some rhizomes are long creeping as shown in

this slide but others are short with stipes

(fronds) growing from them as a single point -

some refer to these as Crowns (see next

slide).

Fern Morphology – Rhizomes and RootsV. Max Brown]

Some ferns have “Crowns” – short rhizome structures, often covered with

scales, from which stipes grow as if from a point source in stead of along a

creeping rhizome.

Mostly glabrous

(smooth), shiny, with a

few scattered hairs

Very fine appressed hair

on secondary rachis

Fern Morphology – Hairs and ScalesV. Max Brown]

Hairs (or Trichomes) and Scales are outgrowths of the epidermis. A simple chain of cells is a Hair while

several rows at the base with a single row at the apex would be a Bristle or Setae and flat sheets of cells are

Scales. In some cases hairs and scales may be Glandular. The types and position of these features on a

fern are often very important in ID of species. Both hairs and scales may be present together.

Dense hairs and

bristles presentHairs common

Hairs

Dense long hairs

Paleae – a Chaffy ( dry,

thin, usually non-green

scale), here on a stipe).

Paleae are formed of

many rows of cells side

by side forming a flat

plate-like scale.

Fern Morphology – Hairs and Scales V. Max Brown]

Flat Plate Scales – may be attached

marginally or centrally by a stalk (if

centrally it is termed a Peltate Scale) –

above scales with dark centers and light

margins, scales here are overlapping

Types of Scales

Scales on

undersurface of

pinnae

Stipe

Sori

Scales tend to

increase in

abundance

toward the lower

portion of the

stem

Fern Morphology – Hairs and Scales V. Max Brown]

Solid and Bicolor Scales - Linear to lanceolate

scales, some all brown (see above) and others

Bicolored - with a dark stripe in the middle and lighter

margins – taken from base of a stipe and rhizome.

Stipe

Types of Scales

Clathrate Scale – lattice-like scale,

here at stipe base.

Other types of scales include Setiferous Scales (scale

margins with hairs or bristles) and Marginate or Flabellate

Scales (scales with margins of a different structure or color)

Fern Morphology – Vascular Structures in StipeV. Max Brown]

The primary Vascular Tissue or Bundles (Stele) within the Stipe are usually set in a supporting tissue.

These Bundles vary in number, shape and arrangement and may help to ID some fern families. In some of

the photographs to follow the CX (cross-sections) were dried for a short time to allow for the supporting tissue

to dry and shrink to better show the vascular bundles.

Stipe CX - Fairly simple and random arrangement of

bundles

Stipe CX – a more systematic arrangement of

bundles

Stipe CX – characteristic X-

shaped vascular bundle of the

Aspleniaceae (spleenwort fern

family)

Fern Morphology – Vascular Structures in StipeV. Max Brown]

Stipe CX – Bracken ferns (Pteridium) often

have “U” or “Ω” shaped vascular bundles.

Stipe CX – characteristic 2

vascular bundles, often

crescent-shaped, typical of the

Thelypteridaceae (Marsh Fern

Family)

A few examples of stipe CX’s aiding in ID of Ferns

Basic Fern Morphology – Reproduction – Dimorphic and Monomorphic Fronds[V. Max Brown]

Sporangia may be on separate fertile fronds

(leaves) from the nutritive or photosynthetic fronds.

These plants have Dimorphic fronds or leaves.

Fertile fronds are termed Sporophylls (often die

earlier and may or may not be photosynthetic).

The non-fertile nutritive or photosynthetic fronds

are termed Trophophylls.

Sporangia may be on normal nutritive or photosynthetic

fronds. These fronds (leaves) are termed Monomorphic.

In many cases (above right) the Sporangia occur on the

upper portion of the nutritive fronds.

Trophophyll

or Nutritive

frondSporophyll or

Fertile frond

Sporangia – the fertile spore-producing

structures of a fern

Sori (clusters of

Sporangia)

Interrupted Fern (Osmunda claytoniana L.) is an example of a fern that have sporangia on modified pinnae in the

middle section of some nutritive or photosynthetic fronds (see photos below).

Basic Fern Morphology – Reproduction – Diamorphic and Monomorphic Fronds[V. Max Brown]

Sporangia on

intermediate

modified portion

of frond giving

the fern its

common name

Basic Fern Morphology – Reproduction – Sori and Sporangia [V. Max Brown]

Sori – clusters of Sporangia which are usually fairly

small and circular to elongate and are usually found on

the under surface of leaves in Monomorphic ferns.

Sporangi may be arranged such that no distinct Sori

(shape of cluster) can be recognized. Sporangia are

are connected to veins for nutrients and elongate Sori

will follow veins. The shape and arrangement of sori

on the leaf are often used in ID of the species.

Sporangia also form on fertile fronds (sporophylls)

of Dimorphic ferns. In some cases modified pinnae

may wrap the sporangia.

Modified pinnae

wrap the sporangia

or spore cases in

this example

Sporangia aligned in

rows along veins on

sporophyll

Sori in systematic patterns on under

surface of fern leaves

Basic Fern Morphology – Reproduction – Sori and Sporangia [V. Max Brown]

Sori (clusters of Sporangia) vary in size, shape, and pattern on the undersurface of monomorphic fern leaves which

helps to define or ID many ferns (in some case the Sporangia may seem to be almost random) – some examples

below.

Almost continuous row of

sporangia along edgeA single row of circular

Sori of sporangia along

each side of midrib

Two rows of circular Sori (looks

almost like uninterrupted sporangia)

along each side of midribOne or more elongate Sori

parallel to pinnate and

forking veins from the midrib

Interrupted Elongate Sori along one

side

One row of elongate Sori mostly

parallel to pinnate veins along

each side of midrib

Sporangia almost completely hidden

and partially protected by hairs

Indusium (plural Indusia) – a thin, epidermal outgrowth, usually translucent and skin-like covering of the Sori found in some

ferns, lacking in others. The Indusia is formed from the area at the base of the sporangia and protects it until the sporangia

mature and burst through by growth. Sometimes the sporangia are partially covered (protected) by the margin of the leaf and

this is termed a False Indusia (both true and false indusial may occur together).

True Indusia

Basic Fern Morphology – Reproduction – True Indusia and False Indusia[V. Max Brown]

Peltate indusia

Basic Fern Morphology – Reproduction – True Indusia and False Indusia[V. Max Brown]

False Indusia

False indusia form by the margin of the leaf rolling under

(revolute) to help protect the spore cases, a true idusium

may also be present in some case.

Annulus

Sporangium

Ruptured Sporangia - spores here

have already dehisced (shot out by

force). The sporangia case is very

thin, in most ferns only a single cell in

thickness.

Basic Fern Morphology – Spore Distribution[V. Max Brown]

Sorus (plural - Sori) – a cluster of Sporangia (a

sac or case that holds the spores) - usually found

on the undersurface of a fern leaf. The stalk that

attaches the individual Sporangium to the leaf is

the Sporangiophore (not shown here).

The Annulus (a row of thick-walled cells) forms a

ring on (around) the sporangium. The ring of cells

is gradually drawn back (contracted) due to

evaporation of water in the Annulus cells and the

sporangium is split open. The spores are shot out

by the cavitation or breaking of the water column in

each of the Annulus cells causing the sporangium

to be rapidly closed acting like a catapult flinging

the spores some distance.

Distribution of Spores by Dehiscence A Sorus

Most fern spores are

disbursed by air currents

(wind) but water may be

effective in some.

Basic Fern Morphology – Spores[V. Max Brown]

Spores can be used in ID of ferns but a microscope is required as the more common smaller spores vary only

from 20-70 microns (1 micron = 0.001 mm or 0.00004 in) and in ferns with larger spores they may only reach a

few hundred microns. They come in a variety of colors from more common yellow, brown and black to white,

orange and green (containing chlorophyll). Most taxonomy keys do not use spores for ID but specialists do use

them and in some cases it may be necessary (discussion of spores will be very brief here).

Most ferns produce one size of small spore and are termed Homosporous. However, Heterosporous ferns

produce two sizes of spores, a larger female spore (with stored food) and a small, short-living male spore – in

these ferns the gametophyte phase actually develops within the spore and cannot use photosynthesis to

produce food. Of the more common homosporous ferns there are two types of spores, Monolete and Trilete

spores.

Monolete spores are shaped somewhat like a bean. During meiosis the spore mother cell divides into four

spores. Imagine a sphere that is cut into half and then each half is again cut into half. Each of the four

segments would have one rounded part and two planar parts that join along a single line where the two planar

parts meet like an apple quartered (one line is exhibited so Monolete).

Trilete spores have four sides, one curved from the outer surface and three flat from inside the spore mother

cell. Imagine a pie with wedge-shaped segments cut (this is two-dimensions). Now imagine a sphere (like a

spherical pie) cut into 4 wedge-shaped segments – each piece has one curved side (from outside) and three flat

sides (each with a line of intersection) meeting at a point in the center of the mother cell (three lines is exhibited

so Trilete).

Monolete Trilete

Use the internet to view images of fern spores and get

a clearer picture of the process of meiosis. A spore

has two layers (outer Exospore and an inner

Endospore). The Perispore, a decorative deposit,

may build up in some species on the outer surface of

the Exospore and may aid ID. Spore viewed from the center of the mother cell

Basic Fern Morphology – Reproduction[V. Max Brown]

Reproduction in the ferns can occur by both Sexual and Asexual means.

SEXUAL REPRODUCTION

Sexual reproduction in ferns is outlined in general in the diagram on the next slide.

Ferns – Sexual Reproduction [V. Max Brown] FERN - SPOROPHYTE GENERATION (2n)

Typically the fern plant we find in the field

Sori containing the Sporangia (spores

develop here in the Sporangium, distributed

mostly by wind, some by water) Diploid Phase (2n)

Haploid Phase (1n)

PROTHALLUS - GAMETOPHYTE GENERATION (1n)

Antheridum

Sperm (1n)

Archegonium

Egg (1n)

Zygote (2n)

(Fertilization)Diploid Phase (2n)

Haploid Phase (1n)

SPOROPHYTE PHASE (2n)

Prothallus grows into a small (~ 6 mm, it varies) heart-shaped photosynthetic

green plant – both male and female structures will form on the prothallus

producing sperm and egg. Various mechanisms attempt to force cross-

fertilization.

Meiosis

Mitosis

First, with Meiosis, the

chromosomes are replicated

(like mitosis) but this

replication is followed by 2

successive cell divisions

resulting in 4 daughter cells

with half the chromosomes as

the parent cell - (1n) or

haploid Spores – cell division

and growth of the Prothallus

is by mitosis keeping the

haploid phase.

Both sperm and egg, (1n) or

haploid, fuse in Fertilization

forming a diploid zygote (2n).

Subsequent cell division in

growth is by mitosis – replication

of chromosomes followed by a

single cell division giving 2

diploid (2n) daughter cells to form

the fern plant.

Spores (1n)

Male structure Female structure

At least a film of water

is necessary for the

sperm to swim to the

egg for fertilization to

occur. The new

sporophyte grows out

from the archegonium.

Alternation of

Generations

*In pteridophytes (ferns and fern allies) the sporophyte phase is the larger and dominate phase whereas with

mosses and liverworts (bryophytes) the gametophyte phase is dominant.

*Some genera have differences from this

general case

Basic Fern Morphology – Reproduction[V. Max Brown]

ASEXUAL REPRODUCTION

Asexual reproduction in ferns is fairly common and the details are far beyond this presentation. The following are some

of the asexual ways ferns propagate.

1 – Apogamy – 32 diploid spores develop instead of 64 haploid spores in the sporangium.

2 – Budding – vegetative buds may develop in some ferns from the stem, leaf, or root.

3 – Hybridization – most hybrids (gametes from different species) are sterile but may reproduce by vegetative means or

become fertile through polypoidy.

4 – Polypoidy – the doubling or multiplication of the number of whole chromosomes.

Phylum Pterophyta – Family Equisetacea has 1 Genus (Equisetum) with about 15 species

worldwide and with about 11 species in North America (some hybrids are also recognized).

Individual species often vary considerably due to environmental factors and many varieties, forms,

etc. have been suggested. These plants have also been called Arthrophytes (jointed plants).

Family Equisetacea – the Scouring Rushes (unbranched or only a few brances) and the Horsetails

(usually much branched in the vegetative phase)

1 – Stems are hollow, jointed with distinct nodes, and some may have branches at the nodes.

Stems grow upward from an apical meristem within each segment (stem between nodes) being

slightly smaller in diameter then the one below (this type of growth is termed Apoxogenesis). A

few species have separate fertile and vegetative stems. The stem is often the main

photosynthetic organ and has air canals.

2 – Leaves are whorled at the nodes, fused at the base with the apex free and resemble teeth.

3 – Spores (homosporous) are green (white in hybrids) and develop in sporangia, within

sporophylls, on cone structures either at the tip of a stem or branch.

4 – The gametophytes are green and unisexual, the male gametophyte is smaller.

5 – Portions of rhizomes may break off and be distributed by water allowing vegetative reproduction.

6 – The horsetails genetically belong to the true “Ferns” and are closely related to the Marattiaceae

(Giant Fern Family)

Phylum Pterophyta – The Horsetails and Scouring Rushes – Definition [V. Max Brown]

Equisetacea – Morphology – Two Types[V. Max Brown]

The Horsetails

The Scouring Rushes

The “Horsetails” are Dimorphic with a Fertile

spore producing phase and a Sterile

vegetative phase that are usually highly

branched giving them their common name.

Fertile phase (some

species have a non-

photosynthetic fertile

phase)

Vegetative

phase

The “Scouring Rushes” are Monomorpic with apical

Strobili (spore producing cone structures). Either no

branches or a few branches may be present (see right

photo above). The stems usually contain silica in the

ridges and were sometimes used as a sort of sandpaper

to clean utensils or sand wood (hence their common

name).

Equisetacea – Morphology – Stem and Leaf Sheath [V. Max Brown]

Stem is hollow in

the internodes but

closed at nodes

Stem is jointed at the nodes.

left photos show the stem

pulled apart at the node.

Right photo the node is

sliced through. The stem

surface is composed of

ridges and grooves (number

of ridges may be used in ID

of some species). Growth of

stem is by lengthening of

internodes.

Leaf sheath (part above

solid node) with black

teeth. Note number of

teeth and ridges match.

Node

Leaf

Sheath

Lower

Internode

Upper

Internode

Equisetacea – Morphology – Stem and Leaf Sheath [V. Max Brown]

The leaf sheath base is at the node and encircles the stem like a collar. The upper part of the sheath consists of

separated teeth that coincide with the number of longitudinal ridges of the stem (number may vary considerably within

a specie). Leaf sheaf color varies from green, gray to white, sometimes with a black or white band, teeth are usually

black and sometimes are shed early.

10 to 14 ridges

(and teeth) in

this species,

teeth large

14 to 50 ridges (and

teeth) in this

species

Sheath

Face Dimensions of sheath –

some keys use the face view

sheath dimensions for ID

(imagine the sheath removed

from stem but do not use the free

part of teeth as part of dimension)

– is it more or less square, or

elongate (longer than wide with

square ends) or elliptical

(elongate with rounded ends)

Stomata (singular Stomate) are

pores for gas exchange and may

be used in ID of some species.

They may be random or in lines

on the surface of the stem or

sunken in lines. Stomata can

usually be observed at 20x

magnification.

Equisetacea – Morphology – Stem Surface and CX [V. Max Brown]

Equisetacea – Morphology – Stem and CX [V. Max Brown]

The size and shape of canals are sometimes used in ID of a

species. The primary longitudinal canals are:

Centrum – large central canal in the pith of the stem.

Vallecular Canals – larger canals beneath the surface valleys.

Carnal Canals – very small canals beneath the surface ridges.

Equisetacea – Morphology – Branching [V. Max Brown]

Branches, when present, sprout or erupt from the bases of the leaf sheaths at nodes. Like the main stem,

branches are usually photosynthetic and have their own nodes, internodes, and leaf sheaths. Secondary

branching is not common but does occur in at least one species. Some species are highly branched, others

rarely or only with a few branches present.

Node with leaf sheath and

teeth on branch. Note that

the balanced branches

sprout at base of leaf

sheath at node of stem.

Some species are highly branched

Some species

are without

branches or

only a few

may be

present (see

photo to left).

2 balanced

branches

from a node

Equisetacea – Morphology – Rhizomes and Roots [V. Max Brown]

Rhizomes are similar to stems and branches in both form and growth. Leaf sheaths are present but in

rhizomes, unlike stems, they are often quite hairy. In addition, in some species tubers may develop from

rhizomes.

Leaf sheath with root hairs

New ascending shoots or

stems from rhizomes

Rhizome CX are similar

to that of aboveground

stems but lacking

chlorophyll

Equisetacea – Morphology – Reproduction [V. Max Brown]

Sporangia

Sporophyll

Immature cone of

E. hyemale

Five to Ten Spores develop in Sporangia on

whorled hexagonal (surface view) Sporophylls

of the Cone (Strobili) structure. The Sporangia

are elongate and split (dehisce) longitudinally.

Cones vary in size from less than 1 cm to 10+

cm and their shape (rounded to sharply pointed)

may be used in ID of species.

Spores vary from 30+ to 70 or so microns, green

in color except in hybrids (white), and are mostly

globose in shape.

Mature fertile cone

of E. arvense

Cones (Strobili, Strobilus) of two different

species of Equisetum

Equisetacea – Morphology – Reproduction – Life Cycle [V. Max Brown]

The Life cycle of Equisetacea is quite similar to Ferns (see slide --). Some differences with

some or all of the ferns are:

1. The Prothallia (gametophyte stage) of Equistacea consist of both male and female gametophytes

(photosynthetic) although sometimes both male and female structures occur on an individual

prothallus. They occur at or above the ground surface. The female prothallia are larger than the

male.

2. Sporangia occur on peltate sporophylls on terminal cones.

3. Spores are Homosporus with 4 elaters (curled filaments). The purpose of the elaters is not clear

but may help in spore dispersal.

4. Gametophytes are photosynthetic.

Phylum Pterophyta – the Psilotaceae (Whisk Fern Family) with 2 Genera (Psilotum and

Tmesipteris) and 4-8 species worldwide, and with 1 genus and 1 species in North America

(Psilotum nudum (Linnaeus) Palisot de Beauvois).

Family Psilotaceae – the Whisk Ferns

1 – The whisk ferns are vascular plants, perennial, terrestrial (with below ground axes anchored by

rhizoids) or epiphytic, roots are absent. Mycorrhizae help with absorption.

2 – Leaves are absent but enations are present (simple small appendages or outgrowths without

veins).

3 – Spores are homosporous, numerous, not green and develop in synangia (2-3 fused sporangia)

either solitary or in axils of appendages.

4 – The gametophyte is subterranean and resembles a small piece of fleshy branched stem.

5 – The Whisk Ferns genetically belong to the true “Ferns” and are related to the

Ophioglossaceae (Adder’s Tongue family)

Phylum Pterophyta – The Whisk Ferns – Definition [V. Max Brown]

Lycophyta (Club-Moss Phylum) consists of 3 Familes

Club Mosses – Lycopodiaceae Family, 7 Genera in NA

Spike Mosses – Selaginellaceae Family, 1 Genus (Selaginella) in NA

Quillworts – Isoetaceae Family, 1 Genus (Isoetes) in NA

The Lycophytes:

1. – Are an old group of seedless vascular plants that split off early from the other vascular plants

and are not closely related to the Ferns.

2. – Are terrestrial (mostly in temperate or boreal habitats) or epiphytic (mostly in tropical habitats).

3. – Have a Microphyll type of leaf (sessile, single vein, simple).

4. – Have life cycles that vary in the 3 families (homosporous or heterosporous) with a single

sporangium on the upper surface of the microphyll or in an axis position between stem and

microphyll.

Phylum Lycophyta – Definition [V. Max Brown]

The Family Lycopodiaceae (The Club Mosses):

1. – Terrestrial or epiphytic, very large and diverse family especially in the tropics, hybridization

common.

2. – Stems may be horizontal or not, upright stems branched or not.

3. – Leaves scale-like and small, simple or may be dimorphic to trimorphic, arranged spirally or

opposite.

4. – Sporangia solitary and located at leaf axils or in clusters in cones (strobili) at branch tips.

5. – Spores homosporous (less than 50 microns), trilete, surfaces decorated (pitted, grooved, etc.)

Gametophytes either underground (not photosynthetic) or above ground (photosynthetic).

Phylum Lycophyta – Family Lycopodiaceae (The Club Mosses) - Definition [V. Max Brown]

Family Selaginellaceae (The Spike Mosses):

1. – Annual or Perennial (sometimes evergreen), herbaceous.

2. – Stems leafy, usually branched or forked, Rhizophores (modified shoots with roots) present or

not).

3. – Leaves scale-like and small, simple or may be dimorphic to trimorphic, single vein.

4. – Sporangia solitary, opening by slits, and located in axils of fertile leaves (Sporophylls – separate

from sterile or vegetative leaves). Sporophyll leaves are in clusters (Strobili) near branch ends.

5. – Heterosporous, a few large spores (greater than 300 microns) and numerous small spores.

Phylum Lycophyta – Family Selaginellaceae (The spike Mosses) - Definition [V. Max Brown]

The Family Isoetaceae (The Quillworts):

1. – Perennial, some evergreen, aquatic to terrestrial (wet conditions), grass-like, with corm-like

rootstock.

2. – Leaves simple, linear, with enlarged base, with 4 longitudinal lacunae (air spaces), a single

vascular strand, and several fibrous bundles, a ligule is present.

3. – Sporangia solitary, located in a basal cavity of leaf with a thin flap or covering (velum).

4. – Heterosporous with Megasporangium (up to hundreds) and Microsporangium (thousands),

surface of spores usually decorated (pits, grooves, etc.). Megagametophytes and

microgametophytes present.

Phylum Lycophyta – Family Isoetaceae (The Quillworts) - Definition [V. Max Brown]