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*. World-wide there are about 25 families, 255+ 1- Lycopodiophyta (Club-Mosses) genera, and perhaps 10,000+ species. In North America there are about 77 genera and 440+ 2- Psilotophyta (Whisk Ferns) species (Flora of North America, V.2). – see 3- Equisetophyta (Horsetails) next slide for more information. 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.
*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 - - PTERIDOPHYTES - The Ferns and their LYCOPODIOPHYTA (CLUB-MOSSES) Allies (number of Lycopodiaceae (Club-moss Family) 10-15 350-400 7 27 2 5 genera and species) Selaginellaceae (Spike-moss Family) 1 700+ 1 38 1 3 for the World, North Isoetaceae (Quillwort Family) 1 150 1 24 1 3 America, and the state EQUISETOPHYTA (HORSETAILS) of Missouri. Equisetacae (Horsetail Family) 1 15 1 11 1 3 Data from The Flora of North America (Vol. 2, 1993) and Flora POLYPODIOPHYTA (FERNS) of Missouri (Vol. 1, 1999) Ophioglossaceae (Adder’s Tongue family) 5 70-80 3 38 2 7 Osmundaceae (Royal Fern Family) 3 16-36 1 3-4 1 3 Gleicheniaceae (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 9-11 Vittariaceae (Shoestring Fern Family) 10 100 1 3 - - Hymenophyllaceae (Filmy Fern Family) 6 650 2 11 - - Dennstaedtiaceae (Family) 20 400 4 6 2 2 Thelypteridaceae (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 8 Dryopteridaceae (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 - - 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]
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.
Blade – leaf portion of Frond, the Axis (stem portion or midrib) of the blade is termed the Rachis
Frond – Stipe and Blade taken together
Stipe - sometimes termed the Stem, supporting Stalk or Petiole of the Frond
Rhizome – “rootstalk” of fern (this is Resurrection Fern [Gray’s Polypody] actually stem-type of tissue, not a true Pleopeltis polypodioides (L.) root) – hidden by moss in upper photo Andrews & Windham subsp. michauxiana (Weath.) Andrews & Windham leopeltis Adventious Roots – true roots growing from the underground stem material (the Rhizomes) – termed adventious because roots do not normally grow from stems Basic Fern Morphology – Leaf Development [V. Max Brown]
Vernation (leaf development)
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). 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 Pinnatifid (compound)
Overall blade shape is important for ID – is it deltoid, lanceolate, etc.; does it taper at both ends or not, etc.
Any difference in orientation of Pinnae (segments) may be important in ID – lower pair of leaves here deflexed
Winged Rachis – not cut to midrib
Segment
Simple blade – may Compound blade – blade is divided (once divided or cut) but be lobed, toothed, etc. not all the way to the midrib leaving a winged rachis. This is but the depth of these termed a Pinnatifid Blade. The individual lobes of the Blade decorations are much are technically termed Segments (lobes not stalked or cut to less than ½ distance to midrib) but are often still called Pinna (Pinnae) (see next midrib. slide for explanation). Fern Morphology – The Blade [V. Max Brown]
Pinnatisect (compound) Pinnate (compound)
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.
Compound blade – blade is divided to the Compound blade – blade is divided to the rachis or midrib. This is termed Pinnate rachis or midrib only at the sinus between (also once divided or cut). Individual lobes. segments are true Pinna (Pinnae). *Warning – the term Segment is often not used in a strict sense Fern Morphology – The Blade [V. Max Brown]
Bipinnate (compound) Pinnate-Pinnatifid (compound)
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). Compound blade – blade is twice divided to the rachis or midrib. This is termed Pinnae and Pinnules are usually Alternate to Bipinnate (also twice divided or cut). Sub-Opposite, sometimes truly opposite. Individual segments are also Pinnules. Fern Morphology – The Blade Tripinnate (compound) [V. Max Brown]
Bipinnate-Pinnatifid (compound)
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
The example at left is pinnate near the tip and Compound blade – blade is twice divided to bipinnate near the base. the rachis or midrib and then partially cut. This is termed Bipinnate-Pinnatifid It is not unusual for a (Pinnules partially cut) species to be described such as this; pinnate to Compound blade - If neither first, second or pinnate-pinnatifid or third divisions reach the axis it would be rarely bipinnate. Tripinatifid (no example shown). Fern Morphology – The Blade [V. Max Brown]
Sometimes it gets difficult to describe with branching of the stipe and rachis
3+ Pinnate (Compound)
Secondary rachis
Upper stipe and rachis divides into 2 main divisions forming In this case the Blade (rachis) is a horizontal fan-shaped or Flabellate Blade. The blade has branched into 3 segments (1st division), several (3-9) secondary rachises each with pinnate and so forth – stem divisions are components in which the segments have incised margins. usually in a horizontal plane Two separate ferns are present in photo above Fern Morphology – Leaflet Features V. Max Brown]
Margins smooth (entire or continuous), apex rounded
Leaflet shape almost ovate (bead-like) with long hairs, margins rolled under (Revolute) Narrow to wide trowel-shaped to lanceolate with Dentate Leaflet long-deltoid with truncate base, teeth (pointed outward) to margin finely Serrate (teeth directed forward) Lacerate (irregular) teeth
Leaflet Auriculate (eared) at base, Leaflets with coarse Serrate teeth Tipped with a Bristle (Serrate - teeth directed forward) serrate with teeth tipped with bristles, segments Coriaceous (Leathery) Fern Morphology – Leaflet Features V. Max Brown]
Some leaves have one “ear” oriented either up or down or, some leaves have 2 symmetrical basal ears.
Fleshy and Glaucous (whitish coating) Acroscopic (ear facing tip or apex Both Acroscopic (facing tip of frond) Auriculate (eared) – so and Basiscopic (facing base) Acroscopic Auriculate. Auriculate (eared)
Margins Erose (irregularly toothed), eared (Acroscopic Auriculate) Fern Morphology – Leaflet Venation Reticulated Veins V. Max Brown]
Free Veins – many pinnately branched from a rachis
Forked veins from midrib, fairly Forked veins without a well-defined simple with one branch (a simple midrib (close to being Dichotomous) vein does not fork)
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.
Dichotomous Veins
Dichotomous veins are found in a few ferns (no midrib). The veins fork from the base Forked veins from midrib, with multiple forking sometimes ending to the tip of the segment with nearly equal at teeth or between teeth angles at each fork. Fern Morphology – Grooved Axes V. Max Brown]
Not grooved on abaxial side
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.
Secondary rachis not grooved on adaxial side of axis Fern Morphology – Rhizomes and Roots V. Max Brown]
Stipe (part of leaf or fronds) 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
True Rootlets
Rhizome (on rock surface), note branching
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 Stipe 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 Rhizome (fronds) growing from them as a single point - some refer to these as Crowns (see next True Rootlets slide). Fern Morphology – Rhizomes and Roots V. 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. Fern Morphology – Hairs and Scales V. 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.
Hairs
Mostly glabrous Hairs common Dense hairs and Dense long hairs Very fine appressed hair (smooth), shiny, with a bristles present on secondary rachis few scattered hairs Fern Morphology – Hairs and Scales V. Max Brown]
Types of Scales
Scales on Sori undersurface of pinnae
Stipe
Scales tend to increase in abundance toward the lower Paleae – a Chaffy ( dry, portion of the thin, usually non-green stem scale), here on a stipe). Flat Plate Scales – may be attached Paleae are formed of marginally or centrally by a stalk (if many rows of cells side centrally it is termed a Peltate Scale) – by side forming a flat above scales with dark centers and light plate-like scale. margins, scales here are overlapping Fern Morphology – Hairs and Scales V. Max Brown]
Types of Scales
Stipe
Clathrate Scale – lattice-like scale, here at stipe base. 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. 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 Stipe V. 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 – a more systematic arrangement of Stipe CX - Fairly simple and random arrangement of bundles bundles Fern Morphology – Vascular Structures in Stipe V. Max Brown]
A few examples of stipe CX’s aiding in ID of Ferns
Stipe CX – characteristic 2 vascular bundles, often crescent-shaped, typical of the Thelypteridaceae (Marsh Fern Family) Stipe CX – characteristic X- Stipe CX – Bracken ferns (Pteridium) often shaped vascular bundle of the have “U” or “Ω” shaped vascular bundles. Aspleniaceae (spleenwort fern family) Basic Fern Morphology – Reproduction – Dimorphic and Monomorphic Fronds [V. Max Brown]
Sporangia – the fertile spore-producing structures of a fern
Sori (clusters of Sporangia)
Trophophyll or Nutritive Sporophyll or frond Fertile frond
Sporangia may be on normal nutritive or photosynthetic fronds. These fronds (leaves) are termed Monomorphic. Sporangia may be on separate fertile fronds (leaves) from the nutritive or photosynthetic fronds. In many cases (above right) the Sporangia occur on the These plants have Dimorphic fronds or leaves. upper portion of the nutritive fronds.
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. Basic Fern Morphology – Reproduction – Diamorphic and Monomorphic Fronds [V. Max Brown]
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).
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 Sporangia also form on fertile fronds (sporophylls) small and circular to elongate and are usually found on of Dimorphic ferns. In some cases modified pinnae the under surface of leaves in Monomorphic ferns. may wrap the sporangia. 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 aligned in rows along veins on sporophyll
Sori in systematic patterns on under surface of fern leaves
Modified pinnae wrap the sporangia or spore cases in this example 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.
Interrupted Elongate Sori along one side Almost continuous row of One row of elongate Sori mostly sporangia along edge parallel to pinnate veins along A single row of circular each side of midrib Sori of sporangia along each side of midrib
Sporangia almost completely hidden Two rows of circular Sori (looks and partially protected by hairs almost like uninterrupted sporangia) One or more elongate Sori along each side of midrib parallel to pinnate and forking veins from the midrib Basic Fern Morphology – Reproduction – True Indusia and False Indusia [V. Max Brown]
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
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. Basic Fern Morphology – Spore Distribution [V. Max Brown]
Distribution of Spores by Dehiscence A Sorus 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.
Most fern spores are Ruptured Sporangia - spores here disbursed by air currents have already dehisced (shot out by (wind) but water may be force). The sporangia case is very effective in some. thin, in most ferns only a single cell in thickness.
Annulus
Sporangium 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).
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, Monolete Trilete 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 *Some genera have differences from this general case
Sori containing the Sporangia (spores develop here in the Sporangium, distributed Diploid Phase (2n) mostly by wind, some by water) Meiosis Haploid Phase (1n) First, with Meiosis, the Spores (1n) chromosomes are replicated (like mitosis) but this replication is followed by 2 successive cell divisions PROTHALLUS - GAMETOPHYTE GENERATION (1n) resulting in 4 daughter cells Prothallus grows into a small (~ 6 mm, it varies) heart-shaped photosynthetic with half the chromosomes as green plant – both male and female structures will form on the prothallus the parent cell - (1n) or producing sperm and egg. Various mechanisms attempt to force cross- haploid Spores – cell division fertilization. and growth of the Prothallus is by mitosis keeping the haploid phase. Antheridum Archegonium At least a film of water is necessary for the Female structure Male structure sperm to swim to the egg for fertilization to occur. The new sporophyte grows out Sperm (1n) Egg (1n) from the archegonium. Haploid Phase (1n)
Mitosis Diploid Phase (2n) (Fertilization) Both sperm and egg, (1n) or haploid, fuse in Fertilization Zygote (2n) forming a diploid zygote (2n). Alternation of Subsequent cell division in growth is by mitosis – replication Generations of chromosomes followed by a SPOROPHYTE PHASE (2n) single cell division giving 2 diploid (2n) daughter cells to form the fern plant. *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. 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 – The Horsetails and Scouring Rushes – Definition [V. Max Brown]
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) Equisetacea – Morphology – Two Types [V. Max Brown] The Scouring Rushes
The Horsetails
Fertile phase (some species have a non- photosynthetic fertile phase)
Vegetative phase
The “Scouring Rushes” are Monomorpic with apical The “Horsetails” are Dimorphic with a Fertile Strobili (spore producing cone structures). Either no spore producing phase and a Sterile branches or a few branches may be present (see right vegetative phase that are usually highly photo above). The stems usually contain silica in the branched giving them their common name. 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 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 Upper of some species). Growth of Internode stem is by lengthening of internodes.
Stem is hollow in Leaf the internodes but Sheath closed at nodes Node
Lower Internode Leaf sheath (part above solid node) with black teeth. Note number of teeth and ridges match. 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.
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)
Sheath
14 to 50 ridges (and 10 to 14 ridges teeth) in this (and teeth) in species this species, teeth large Equisetacea – Morphology – Stem Surface and CX [V. Max Brown]
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 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.
Some species are highly branched
Some species are without branches or Node with leaf sheath and only a few teeth on branch. Note that may be the balanced branches present (see sprout at base of leaf photo to left). sheath at node of stem.
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.
New ascending shoots or stems from rhizomes
Leaf sheath with root hairs
Rhizome CX are similar to that of aboveground stems but lacking chlorophyll Equisetacea – Morphology – Reproduction [V. Max Brown]
Cones (Strobili, Strobilus) of two different species of Equisetum
Sporophyll
Sporangia
Five to Ten Spores develop in Sporangia on whorled hexagonal (surface view) Sporophylls Immature cone of of the Cone (Strobili) structure. The Sporangia E. hyemale 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 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 Whisk Ferns – Definition [V. Max Brown]
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 Lycophyta – 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 – Family Lycopodiaceae (The Club Mosses) - 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 Selaginellaceae (The spike 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 Isoetaceae (The Quillworts) - 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.