"Ferns and Fern Allies;"
usually photosynthetic, but without vascular tissue, cuticle, and stomates,
and hence inconspicuous and small (101 cm), confined to relatively
male and female gametangia, i.e. antherida and archegonia, respectively.
Male gametes flagellated, female gametes sessile, within archegonium.
Fertilization depends upon the availability of a film of liquid water
within which sperm can swim to the archegonia (illustrations not
to same scale, redrawn from Sporne 1975; images of prepared slides © 2009 Royal Ontario Mueum).
of the gametophyte at maturity, photosynthetic, with vascular
tissue, cuticle, and stomates, and hence varying considerably in size
(101 - 103 cm) and complexity.
spores in sporangia classified according to their development as
eusporangiate or leptosporangiate (compare diagrams above, below). Spores
all of one size (homosporous), or of two sizes (large, small; heterosporous).
today by a variety of growth habits (life forms), hence occupying
a wide range of habitats, notwithstanding the dependence on the availability
of liquid water for sexual reproduction.
- aquatic (Marsileales,
- arboreal (Dicksoniaceae;
- sometimes extremely
weedy, e.g. bracken (Pteridium aquilinum)
- ...as a group,
much more abundant and diverse during the latter part of the Paleozoic
and the Mesozoic than presently.
occurs via spores, of whatever kind, i.e. by single cells however
- ...have only recently been examined in light of thinking about the theoretical importance of outcrossing.
- Work in the 1970s documenting the breeding systems of homosporous ferns has provided an impetus for new questions about gametophyte biology and cytogenetics in these plants
- Haufler CH (2014) Ever since Klekowski: Testing a set of radical hypotheses revives the genetics of ferns and lycophytes. American Journal of Botany 101: 2036-2042. [Open Access]
- The life cycle of ferns has also been the subject of revisionary comments about the way it is taught; see Haufler CH, Pryer KM, Schuettpelz E, Sessa EB, Farrar DR, Moran R, Schneller JJ, James E. Watkins J, Windham MD (2016) Sex and the Single Gametophyte: Revising the Homosporous Vascular Plant Life Cycle in Light of Contemporary Research. Bioscience 66: 928-937.
[not Open Access, unfortunately]
- ...is the production
of (two) different kinds of spores; microspores and megaspores.
germinates to give rise to female gametophyte; microspore to male
gametophyte, in both cases the gametophytes being retained within the
- ...male prothallus
reduced to a single antheridium from which varying numbers of motile
sperm are released.
- ...female prothallus
develops first by free-nuclear divisions, often while the megaspore
is still in the sporangium. Cell walls are then laid down and archegonia
and rhizoids develop as the spore wall ruptures.
results in development of an embryo sporophyte, initially still
within the wall of the megaspore.
- ...modern examples
and Isoetes (Lycopodiophyta), and the water ferns (Marsileales,
are plant families? | How do we distinguish
them? | How and why do we study them? |
Selected vascular plant families of Ontario
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2008 Department of Ecology & Evolutionary Biology and 2000-2006 Botany Department, University of Toronto.