BEN # 122
aceska at CUE.BC.CA
Sat Dec 16 10:28:53 EST 1995
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No. 122 December 16, 1995
aceska at freenet.victoria.bc.ca Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
IN SEARCH OF THE FERN SEED (PART 3 OF 3)
From: "Robbin C. Moran" <biobrm at aau.dk>
originally published in the Fiddlehead Forum 22: 37-40. 1995
We smile at these questions today, knowing that they are com-
pletely misguided, but they were valid questions to botanists in
the 1700s and early 1800s. It wasn't until 1844 that Karl von
Naegeli, a German botanist, steered questions about the fern
seed in the right direction. By focusing his microscope on the
undersurfaces of the prothalli (the membranes or scales that
Lindsay originally reported), von Naegeli saw globose papillae
containing dark, spiral filaments. He noticed that the papillae,
when wet, burst at the tip and released the spiral filaments,
which then began to wiggle and swim away. He knew that similar
papillae and filaments had been found in mosses and liverworts,
where they were called antheridia, in allusion to the "male"
anther of the flower. Thus, von Naegeli adopted the name an-
theridia for the papillae he saw on fern prothalli. But where
did the spiral filaments swim to?
This question was answered in 1848 by Michael Jerome Leszczyc-
Suminski, a Polish count with a botanical bent. He found that
the spiral filaments swam to another kind of papilla also lo-
cated on the undersurface of the prothalli. This type of
papilla, which we now call an archegonium, was flask-shaped with
a long neck and a single, large cell at the base. When the sperm
swam to the archegonium, they wiggled downwards between the neck
cells and penetrated the large basal cell. After penetration,
this cell (now known to be an egg cell) developed into an
embryonic fern with roots, stem, and leaves. This baby plant
eventually grew into a mature fern with spore-bearing leaves.
What developed from Leszczyc-Suminski's observations was the
picture of fern reproduction still taught today. In a series of
quick nutshells this is it: The spores (fern dust) are produced
on the undersides of the leaves in sporangia. They are liberated
from the sporangia, land on a suitable substrate, and germinate.
They grow into prothalli that bear the sex organs-archegonia and
antheridia-which produce egg and sperm, respectively (the
prothalli of some ferns produce only one kind of sex organ). The
sperm are released from the antheridia when water is present and
swim to the archegonia and fertilize the egg. The resulting
cell, the zygote, develops into an embryo with stem, roots, and
leaves. This embryo grows by widening its stem and producing
larger and larger leaves until a spore-bearing leaf eventually
appears. At this point the process is complete.
This sequence of events is known as the fern life cycle-the
bugbear of many Introductory Botany students. It has two dis-
tinct phases, or generations. The first is called the
gametophyte generation because it produces the gametes or sex
cells. The second is called the sporophyte generation because it
produces the spores. The gametophyte consists of the prothallus,
and the sporophyte consists of the "normal" fern plant we typi-
cally think of-the one with roots, stems, and leaves. Each
generation develops from a single cell: the gametophyte from a
spore, the sporophyte from a zygote.
One point must be made about these two generations, a point
often dimly understood: The gametophyte is the sexual generation
because it produces the sex cells, egg and sperm. In contrast,
the sporophyte is the asexual generation because it produces
asexual spores; it does not produce sex cells. Remember this the
next time you spot a leafy fern luxuriating in the wild. What
you are looking at is an asexual being, one that does not and
cannot engage in sex. This point is difficult to grasp because
we tend to equate, erroneously, our own bodies with that of the
fern sporophyte. But unlike plants, humans and other animals
produce their gametes directly by meiosis; we have no interven-
ing gametophytic (sexual) stage that produces gametes by
But to return to the fern-seed. Botanists today realize that
spores and seeds are completely different structurally. A spore
consists of a single cell and contains no preformed embryonic
parts. In contrast, a seed (typically) consists of hundreds or
thousands of cells and contains stored food (the endosperm) and
an embryo. Moreover, spores and seeds differ in what they give
rise to. A fern spore gives rise to the prothallus of the
gametophyte generation; a seed, to the baby plant of the new
These differences between spores and seeds seem so great that
most of us are astonished when we learn that early botanists
once seriously considered spores were seeds. But our astonish-
ment is only proof that botany has progressed. Nowadays, it is
the belief in the fern seed that walks invisible.
Selected References and Notes.
The history of ideas about sexual reproduction in plants and
animals, especially how it reflects prevailing social attitudes
about sex, is treated by John Farley, Gametes & Spores, Ideas
about Sexual Reproduction, 1750-1914 (Baltimore: The Johns
Hopkins University Press, 1982).
John Lindsay described his observations on fern reproduction in
"Account of the Germination and Raising of Ferns from the Seed,"
Transactions of the Linnean Society 2: 93-100 (1794).
The life of Leszczyc-Suminski is documented by Cezary W.
Domanski in "M.J. Leszczyc-Suminski (1820-1898), an Unknown
Botanist-Discoverer," Fiddlehead Forum 20: 11-15 (1993).
Author's address: Dr. Robbin C. Moran, Dept. of Systematical
Botany, University of Aarhus, Denmark
UNIVERSITY OF BRITISH COLUMBIA HERBARIUM CLOSED FOR FUMIGATION
From: Olivia Lee <ubc at unixg.ubc.ca>
University of British Columbia Herbarium (UBC), Vancouver, B.C.
will be closed for fumigation from December 18, 1995 to January
NEW RECORDS OF LICHENS FROM THE QUEEN CHARLOTTE ISLANDS
Brodo, Irwin M. 1995. Lichens and lichenicolous fungi of the
Queen Charlotte Islands, British Columbia, Canada. 1.
Introduction and new records for B.C., Canada and North
America. Mycotaxon 56: 136-173.
Abstract. The Queen Charlotte Islands lie off the west coast of
North America, and are characterized by a strongly oceanic
climate, coniferous rain forest and rocky shores, with a low
mountainous region raising to 1100 m. Its lichen flora is abun-
dant and diverse, with numerous disjunctions and new taxa.
Fifty-four crustose lichens and lichenicolous fungi are reported
as new for British Columbia, among them six are new to Canada,
and 18 are new to the North American flora. The new combination
Porpidia ochrolemma (Vain.) Brodo & R. Sant. is made.
[The most interesting reports: Lecidea crassilabra - previously
known only from Australia and New Zealand; Pyrenopsis tasmanica
- previously known from Tasmania and New Zealand.- AC]
HAVE A NICE HOLIDAY SEASON AND ALL THE BEST IN 1996! - A. CESKA
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