Ferns

 

Classification

There are many problems in fern classification and no widely accepted classification of the ferns has yet been published. The major problems are associated with the great antiquity of the ferns and the high rates of extinction and evolution (convergent and divergent). In a conservative approach to fern classification (Kubitzki 1990) recognized 33 families.

Fern morphology

The mature fern plant or sporophyte has the same parts as most plants: roots, rhizomes (stems) and fronds (leaves). Except for tree ferns, the ferns are dominated by their fronds.

The fronds can be divided into two parts: the stipe (petiole) and the blade (leafy part of frond). The blade can can range from simple and undivided to finely dissected. Where the blade is not cut to the midvein it is called pinnatisect. In pinnate fronds the blade is divided into leaflets. In divided fronds the main axis is called the rachis. thiner divisions are called pinnules or segments. Where the blade is further dissected terms as bipinnate, tripinnate etc. are used.

illustration of some useful terms and leaf shapes ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

In all/most species of ferns the surface of rhizome, stipe and fronds are protected by outgrowth from the surface of these structure. This protective indumentum is called either hairs or scales.

Scales of Ferns ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

The Sorus

The sporangia (or spore case) are borne on the back or margins of the fronds. They are usually grouped together in small clusters called sori. The arrangement of the sorus and its shape are important in Fern identification and are usually necessary for identification of a plant. In many genera there is a protective flap of tissue covering the young sorus. When the sorus is marginal, it is often called protected by the recurved margin of the frond. This recurved margin is called a false indusium, but in Adianthum the sporangia are borne on the lower side of the flap.

Protective structures in the sorus: Paraphyses (superficially like hairs) are either single stalked or branched. They are very useful taxonomically for identification at species level.

Cross section through Sori ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

Shapes of Fern indusia ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

The Sporangia

The sporangium of most ferns is a thin walled case usually borne on a stalk. A row of thick-walled cells, the annulus, functions to open and rapidly close the sporangium when the spores are mature. The position of the annulus differs and in the more primitive families is arranged diagonally, near the tip or on the side of the sporangium.

The process of spore shedding ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

The gametophytic stage

The gametophytic stage of the life cycle develops from the spore produced by reduction division in the sorus of the sporophte. The spore initially develops into a filamentous prothallus, but within a few weeks further develops in most groups into a heart-shaped structure. This is one cell thick, except for the archegonial cushion and the male organs (antheridia) are found on the basal margins of the prothallus.

Fern prothallus and sex organs ( Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' )

Fern Diversity on Madeira island
Adianthum reniforme (Pteridaceae)
Adianthum reniforme (Pteridaceae)
Adianthum hispidulum (Pteridaceae)
Asplenium hemionitis (Aspleniaceae)
Davallia canariensis (Davalliaceae)
Davallia canariensis (Davalliaceae)
Woodwardia radicans (Blechnaceae)
Woodwardia radicans (Blechnaceae)
Fern Diversity in New Zealand South Island
Blechnum discolor (Blechnaceae)
Cyathea sp. (Cyatheaceae)
Pyrrosia eleagnifolia (Polypodiaceae) on drift wood
Pyrrosia eleagnifolia (Polypodiaceae)
Trichomanes reniforme (Hymenophyllaceae)
Trichomanes reniforme (Hymenophyllaceae)
sticherus cunninghamii (Gleicheniaceae)
sticherus cunninghamii (Gleicheniaceae)
Asplenium septentrionale (Aspleniaceae) growing in the Pyrenees
Asplenium septentrionale (Aspleniaceae)
Asplenium septentrionale (Aspleniaceae)

Bibliography

Judd, W.S.; Campbell, C.S.; Kellogg, E.A.; Stevens, P.F. 1999. 'Plants systematics, a phylogentic approach' Sinauer Associates Inc. Publ. , Sunderland, 464p.

Raven, P.H., Evert, R.F. 2003 'Biology of Plants' 6th ed. W.H.freeman and company worth Publisher, 944p.

Kenrick, P. & P. Davis. 2004. 'Fossil Plants' Natural History Museum, London. 216p.

Johns, R.J., 1996. 'An Introduction to the Ferns and Ferns Allies' Kew personal communication.

 

Home page

Classification

Fern morphology

The Sorus

The Sporangia

The gametophytic stage

practical

Bibliography

Practical

Selaginellaceae. Selaginella fissidentoides

Dryopteridaceae Dryopteris prothalus slide preparation

Polypodiaceae. Microgramma

Adianthaceae Adiantum sp.

Dryopteridaceae Arachniodes standishii

Davalliaceae Humata sp

Lygodium spores germination

     

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Order

Family

Species Number

Lycophytes

 

Lycopodiaceae

 
     
       

Ferns

Ophioglossales

Ophioglossaceae

80

Ferns

Psilotales

Psilotaceae

12

Ferns

Equisetales

Equisetaceae

15

Ferns

Marattiales

Marattiaceae

150

Ferns

Osmundales

Osmundaceae

20

Ferns

Hymenophyllales

Hymenophyllaceae

600

Ferns

Gleicheniales

Gleicheniaceae

125

Ferns

Gleicheniales

Dipteridaceae

11

Ferns

Gleicheniales

Matoniaceae

4

Ferns

Schizaeales

Lygodiaceae

25

Ferns

Schizaeales

Anemiaceae

100

Ferns

Schizaeales

30

Ferns

Salviniales

Marsileaceae

75

Ferns

Salviniales

Salviniaceae

16

Ferns

Cyatheales

Thyrsopteridaceae

1

Ferns

Cyatheales

Loxomataceae

2

Ferns

Cyatheales

Culcitaceae

2

Ferns

Cyatheales

Plagiogyriaceae

15

Ferns

Cyatheales

Cibotiaceae

11

Ferns

Cyatheales

Cyatheaceae

600

Ferns

Cyatheales

Dicksoniaceae

30

Ferns

Cyatheales

Metaxyaceae

2

Ferns

Polypodiales

Lindsaeaceae

200

Ferns

Polypodiales

Saccolomataceae

12

Ferns

Polypodiales

Dennstaedtiaceae

170

Ferns

Polypodiales

Pteridaceae

950

Ferns

Polypodiales

Aspleniaceae

700

Ferns

Polypodiales

Woodsiaceae

700

Ferns

Polypodiales

Thelypteridaceae

950

Ferns

Polypodiales

200

Ferns

Polypodiales

Onocleaceae

5

Ferns

Polypodiales

1700

Ferns

Polypodiales

Lomariopsidaceae

70

Ferns

Polypodiales

Tectariaceae

230

Ferns

Polypodiales

Oleandraceae

40

Ferns

Polypodiales

65

Ferns

Polypodiales

1200

Ferns

9118

 

SELAGINELLACEAE Selaginella fissidentoides (Hook.& Grev.) Spring





Find strobili and isolate a mega and a microsporangia. Observe mega and microspores. Leaf arangment and adaptation.

blue irridescence in Selaginella wildenowii 1994-1186
strobili
strobilus with sporangia  
strobilus
megasporangium
megaspores and microspores picture of a branch with micophylls

 

Observe through high magnification the Dryopetris Prothallus slide preparations.

 

observe antheridium, archegonium and rhizoids

you may have to play with the focus to see the archegonia

 

 

 

Is this the Gametophyte or Sporophyte ?

A gametophyte

 

Dryopteris Prothallus seen with a high magnification microscope
Dryopteris Prothallus x40
Antheridium seen with a high magnification microscope Archegonium seen with a high magnification microscope Archegonium seen with a high magnification microscope

 

Woodwardia unigemmata.


BLECHNACEAE

Observe sori, sporangia, and scales on leaves and rhizomes.

 

abaxial frond surface sorus without indusium sorus
bulbil Picture of a rhizome scale

 

Microgramma sp.

Natural Source
POLYPODIACEAE Microgramma

Observe sori, sporangia, paraphyses and scales on leaves and rhizomes.

 

Drawing of the plant with fertile and sterile Fronds Scales on leaves and rhizomes
Darwing of the sporangia and paraphyse inside a sorus
Picture of a sorus Picture of a leaf scale

 

Adianthum sp.



Observe False indusium and sporangia.

Adianthum leaf segment False indusium
Sporangia
sporangia sporangium sporangium

 

Arachniodes standishii (T.Moore) Ohwi

Range: Japan
Japan

Observe indusium, sporangium and scales on stipe.

Adaxial frond surface Sori mature sori
Sori
sporangia scales on stipe

 

Humata sp.


DAVALLIACEAE


Geography: Peninsular Malaysia Findspot: Sabah

Observe sori, sporangia and scales on rhizome.

rhizome with scales
frond abaxially
rhizome and fronds scale
sori

 

Isolate spores of Lygodium and let then germinate in a petri dish containing soaked filter paper. Leave the petri dish in a bright place for two weeks before first observations.

Lygodium japonicum


SCHIZAEACEAE Lygodium japonicum Sw.

Range: China, Australia
India, SE Asia to N Australia

Isolate spores of Lygodium and let them germinate in a petri dish containing soaked filter paper. Leave the petri dish in a bright place for two weeks before first observations.

Fertile frond adaxially sori with indusium
sporangium spores

Week 1 Week 12
Week4 Week 4 Week 12 Week 12

 

 

Practical

Selaginellaceae. Selaginella fissidentoides

Dryopteridaceae Dryopteris prothalus slide preparation

Polypodiaceae. Microgramma

Adianthaceae Adiantum sp.

Blechnaceae woodwardia unigemmata

Dryopteridaceae Arachniodes standishii

Davalliaceae Humata sp

Lygodium spores germination