Garden Wildplants
             Garden Wildplants
Ferns and horsetails
 
These plants occupy a developmental stage considerably more complex than mosses and liverworts, but not as sophisticated as flowering plants.  Unlike mosses, they have vascular tissue (xylem and phloem), but they reproduce, like mosses, using spores not seeds, and have a complex life cycle with both diploid and haploid phases.
 
Botanically, they are members of the Class Polypodiopsida  which in addition to true ferns, contains the adder's tongue and relatives, the horsetails and a further purely tropical group. An older term you will come across is Pteridophytes, which further included the lycophytes, an ancient (but still living) group now classed separately which includes the clubmosses which are largely confined to high ground and poor soils.
 
Life cycle
 
Ferns have two life stages, which differ in the number of chromosomes in their cells. In “higher” plants and most animals, the dominant or main life stage is diploid – with two copies of each chromosome, one from its female and one from its male parent. A haploid cell or organism has only a single set of chromosomes.  To reproduce sexually, diploid organisms first need to halve the chromosome count, producing haploid eggs and sperm. When these come together and fuse, the diploid chromosome count is restored and an embryo can form.
 
In ferns and horsetails the dominant life phase is also diploid, and called the sporophyte which produces abundant haploid spores in structures called sporangia. The spores settle and germinate to produce a separate haploid  gametophyte generation, which is inconspicuous and short-lived, but which produces sperm and eggs. When fertilised the embryos grow up into the much larger sporophyte stage.  Mosses and liverworts do much the same, but in their case it is the gametophyte which is dominant.
 
 
 
 
       Garden Wildplants
             Garden Wildplants
Prothallus, the gametophyte stage of the giant tree-fern Dicksonia, just a few millimetres in size.
Ferns  Subclass  Polypodiidae  
 
We cover garden ferns in our page here.  As a group they are easily recognised, with substantial, often quite coarse green usually pinnate leaves or fronds, arising from a basal rosette, which can grow upwards with time by growing new leaf whorls, and can become substantial "tree-ferns", but these are not native to Britain and Ireland, although are spreading in Cornwall and County Kerry following Victorian introductions.1.
 
Fern fronds can be simple tounge-shapes, or of complex form with leaflets arising from successive orders of midrib branching.  They produce their spores in sporangia grouped into clusters called "sori" under a cap called an "indusium" beneath mature fronds, and the shape of these often dark coloured structures is helpful in species identification.
 
 
 
Horsetails:  Left: Typical view of the main (sporophyte) phase  Right: showing stems with strobili
 
There are few living horsetail species, but the group was immensely important back in the Palaeozoic era, and during the Carboniferous period (c 360-300 million years ago), the 50m tall Calamites horsetails formed a large proportion of our coal deposits.
 
References
 
Stace, C. and Crawley, M.J. (2015) Alien Plants.  New Naturalist HarperCollins p.372
 
Books and websites
 
Merryweather, J. (2019) Britain's Ferns:A Field Guide to the Clubmosses, Quillworts, Horsetails and Ferns of Great Britain and Ireland. Princeton University Press
 
British Pteridological Society website 
 
 
 
Page written and compiled by Steve Head
Common male-fern Dryopteris filis-mas frond, and (right) spore-producing sporangia clustered into sori under a frond.
 
Ferns (including related extinct groups) were important landplants in the palaeozoic era and contributed to the laying down of the Carboniferous coal measures.
 
Horsetails Subclass Equisetidae 
 
We have a page on horsetails here. The horsetails are a sister group to the ferns, but profoundly different in appearance, and they probably diverged before the other members of the Polypodiopsida  separated. Their life cycle is very like that of the ferns, with spores germinating to produce a small haploid gametophyte prothallus producing eggs and sperm, which when fertilised will produce the next dominant sporophyte generation.
 
The name horsetail comes from the very characteristic shape of the plant, which has a thick hollow photosynthetic stem, with whorls of thin leaves, which are often not photosynthetic.  Many bear whorls of thin side stems too, making the plant appear bushy and like a horse's tail. The sporangia are carried on  swollen cone-like structures called strobili at the end of the stem, raised up high for dispersal, often on separate stems from the green foliage..
Ferns and horsetails
 
These plants occupy a developmental stage considerably more complex than mosses and liverworts, but not as sophisticated as flowering plants.  Unlike mosses, they have vascular tissue (xylem and phloem), but they reproduce, like mosses, using spores not seeds, and have a complex life cycle with both diploid and haploid phases.
 
Botanically, they are members of the Class Polypodiopsida  which in addition to true ferns, contains the adder's tongue and relatives, the horsetails and a further purely tropical group. An older term you will come across is Pteridophytes, which further included the lycophytes, an ancient (but still living) group now classed separately which includes the clubmosses which are largely confined to high ground and poor soils.
 
Life cycle
 
Ferns have two life stages, which differ in the number of chromosomes e
in their cells. In “higher” plants and most animals, the dominant or main life stage is diploid – with two copies of each chromosome, one from its female and one from its male parent. A haploid cell or organism has only a single set of chromosomes.  To reproduce sexually, diploid organisms first need to halve the chromosome count, producing haploid eggs and sperm. When these come together and fuse, the diploid chromosome count is restored and an embryo can form.
 
In ferns and horsetails the dominant life phase is also diploid, and called the sporophyte which produces abundant haploid spores in structures called sporangia. The spores settle and germinate to produce a separate haploid  gametophyte generation, which is inconspicuous and short-lived, but which produces sperm and eggs. When fertilised the embryos grow up into the much larger sporophyte stage.  Mosses and liverworts do much the same, but in their case it is the gametophyte which is dominant.
 
 
 
 
Ferns  Subclass  Polypodiidae  
 
We cover garden ferns in our page here.  As a group they are easily recognised, with substantial, often quite coarse green usually pinnate leaves or fronds, arising from a basal rosette, which can grow upwards with time by growing new leaf whorls, and can become substantial "tree-ferns", but these are not native to Britain and Ireland, although are spreading in Cornwall and County Kerry following Victorian introductions.1.
 
Fern fronds can be simple tounge-shapes, or of complex form with leaflets arising from successive orders of midrib branching.  They produce their spores in sporangia grouped into clusters called "sori" under a cap called an "indusium" beneath mature fronds, and the shape of these often dark coloured structures is helpful in species identification.
 
 
 
Prothallus, the gametophyte stage of the giant tree-fern Dicksonia, just a few millimetres in size.
Common male-fern Dryopteris filis-mas frond, and (right) spore-producing sporangia clustered into sori under a frond.
 
Ferns (including related extinct groups) were important landplants in the palaeozoic era and contributed to the laying down of the Carboniferous coal measures.
 
Horsetails Subclass Equisetidae 
 
We have a page on horsetails here. The horsetails are a sister group to the ferns, but profoundly different in appearance, and they probably diverged before the other members of the Polypodiopsida  separated. Their life cycle is very like that of the ferns, with spores germinating to produce a small haploid gametophyte prothallus producing eggs and sperm, which when fertilised will produce the next dominant sporophyte generation.
 
The name horsetail comes from the very characteristic shape of the plant, which has a thick hollow photosynthetic stem, with whorls of thin leaves, which are often not photosynthetic.  Many bear whorls of thin side stems too, making the plant appear bushy and like a horse's tail. The sporangia are carried on  swollen cone-like structures called strobili at the end of the stem, raised up high for dispersal, often on separate stems from the green foliage..
Horsetails:  Left: Typical view of the main (sporophyte) phase  Right: showing stems with strobili
 
There are few living horsetail species, but the group was immensely important back in the Palaeozoic era, and during the Carboniferous period (c 360-300 million years ago), the 50m tall Calamites horsetails formed a large proportion of our coal deposits.
 
References
 
Stace, C. and Crawley, M.J. (2015) Alien Plants.  New Naturalist HarperCollins p.372
 
Books and websites
 
Merryweather, J. (2019) Britain's Ferns:A Field Guide to the Clubmosses, Quillworts, Horsetails and Ferns of Great Britain and Ireland. Princeton University Press
 
British Pteridological Society website 
 
 
 
Page written and compiled by Steve Head