Table Of ContentBryophyteSpecialIssue
Introducing bryophytes
Maria Gibson
PlantEcologyResearchUnit,SchoolofLifeandEnvironmentalSciences
DeakinUniversity,221 BurwoodHighway,Burwood,Victoria3125
Bryophytesaresmall butbeautiful plants. This special issue of The Victorian
They are frequently overlooked yet are Naturalist highlights some of the current
vital components ofmost ecosystems. investigative work being done in Victoria.
Bryophytes are early colonizers after dis- Papers included in this issue consider the
turbancee.g. by tire (Fig. 1),protectingthe soil crusts of the Little Desert National
bare soil and nutrient-rich ash from wind Park and their associated invertebrates, a
and water erosion, and providing a moist comparison ofthe epiphytic bryophytes of
bed for seed germination of vascular Myrtle Beech with those ofMountain Ash,
plants. They contribute tonutrient cycling, the bryophytes of Cool Temperate
provide shelter and protection for inverte- Rainforest, and bryophytes of stream
brates-and thus harboura foodsource for rocks,
a wide variety ofanimals - and provide Bryophytesaredivided into threegroups,
nesting material for birds and cocoon- the mosses, liverworts and hornworts.
forming insect larvae. They have been None of them has roots; instead, they
used as bioindicators and biomonitors of attach to their substratum by rhizoids
environmental pollution as well as phy- which do not lake up nutrients as roots do.
toremediators, and a number ofthem have Bryophytes take up nutrients dissolved in
antifungal and antibacterial properties. In water directly through the plant body.
spiteofall this, relativelylittle is known of Mosses have stems and leaves (Fig.2),
bryophyte ecology or, indeed, what occurs while liverworts consist of stems and
where. leaves or a thallus consisting of flattened
sFiigo.n 1a.nFdunparorviiadhinyggraommeotirsitcah,aabimtaotssf,orforremgsentehriactkiocnaropeftsotahfetrerplfiarnet,s.prTotheectpihngottohgeraasphhbweadsftraokmeneroa-t
WilsonsPromontory,approximatelysixmonthsaftertheeasterbushfire.
192 The Victorian Naturalist
BryophyteSpecialIssue
green strap-like orlobed structures (Figs. 3
and 4). Moss leaves often have a vein
(costa) running down the centre. Leafy liv-
erworts never have a costa. The leaves of
bothmosses and liverworts usually areone
cell in thickness, although some mosses
have more cell layers, especially around
the costa. Liverwort leaves are often two-
lobed, with each lobe growing from two
distinct apical points. Most moss species
have leaves arranged around the stem in a
spiral. Leafy liverworts have leaves
arranged in rows; many have two rows of
lateral leaves and a row ofsmaller leaves
on the undersurface. Mosses have multi-
cellular rhizoids; liverworts have unicellu-
larrhizoids.
Hornworts are thallose, so superficially
resemblethalloid liverworts, but many fea- Fig. 2. Cyathophorum bulbosum a mosswith a
tures distinguish the two. Each hornwort leafarrangement common in le,afy liverworts,
cell usually has only one large chloroplast, i.e. two lateral rows ofleaves and a row of
but liverwort cells have many small dis- smallerleavesontheundersurface(notshown).
coid chloroplasts. Hornworts have stomata
but liverworts do not. These features, how-
ever, are difficult to see in the field.
Hornworts are often rosette-like and oneto
two centimetres across. Usually they have
many internal cavities filled with
mucilage, which can be seen with a han-
dlers by slicing through the hornwort and
looking at the cut edge. In liverworts such
cavities are airfilled.
Many otherfeatures can be used to distin-
guish the three groups ofbryophytes. Most
ofthese require microscopic analysis, but
with a little practice it is surprising how
quickly one intuitively recognizes whether Fig.3 Marchantiabertoroana acommonthal-
a bryophyte is a moss, liverwort or horn- loid liverwort. ,
wort. Identifying a bryophyte to genus or
species level ismoredifficult. Overthe last
tenyears,the increasedproduction ofbeau-
tifully illustrated field guides with many
accompanying photographs has helped
greatly, but photographs frequently are
insufficient to distinguish a bryophyte to
either genus or species level. The serious
student of bryophytes requires simple,
easy-to-use keys. This issue of The
Victorian Naturalist presents several keys,
one to the genera (and many species) of
leafy liverworts, one to the thallose liver-
worts and hornworts and one to the moss
genus Fabronia. The paper dealing with
aFfafbinriotnietsaaanldsocoinnscelruvdaetsioandsitsactuuss.sion on its tFhiagl.lo4s.eHliyvmerewnoortphcyotmomnofnlaibnewleltatfuomr,estas.stalked
Vol. 123 (4) 2006 193
BryophyteSpecialIssue
Bryophytes can reproduce sexually and duces budsthatgrow into leafy plants with
asexually (without sex). Asexual reproduc- rhizoids. In liverworts, the protonemal
tion is generally vegetative and includes stage is reduced and each protonema pro-
fragmentation with subsequent growth of duces only a single plant. Protonema do
the fragment into a new plant, develop- not occur in hornworts. Sporophytes easily
ment of specialized structures such as distinguish the bryophyte groups from
gemmae, which grow into new individuals, each other but, inconveniently, are not
and new growth ofshoots that develop rhi- always present. Some species never pro-
zoids and become independent following duce sexually so never produce a sporo-
degeneration ofolder parts. Sexual repro- phyte. Other species may reproduce sexu-
duction involves an alternation ofgenera- ally in one region but not another. Studies
tions (Fig. 5). The green plant normally on the sexual reproduction of bryophytes
recognized as the bryophytic plant is the are comparatively few worldwide but are
gametophyte generation, which produces particularly rare in Australia. This issue
the gametes, that is, the eggs (ova) and presents an investigation of the sexual
sperm (antherozoids). Fertilization of the reproduction ofAtriehum androgynum, a
egg results in development of the second common moss ofwet forests in Australia.
generation,calledasporophyte,whichpro- Also included in this issue is a paper
duces the capsule that contains spores. dealing with the bryophyte collection of
Sporophyte cells have twice the chromo- the National Herbarium of Victoria. This
some (genetic material) component of the paper provides a historic timeline ofthe
gametophyte. Within the capsule a process collectionsand providesdetailsonsome of
called meiosis occurs, resulting in develop- themoresignificant collectors.
ment ofspores that have halfthe chromo- This landmark issue of The Victorian
some complementofthe sporophyte. Upon Naturalist showcases some ofthe research
release and dispersal to a suitable habitat, occurring throughout Victoria and should
the spores germinate and develop into encourage others to look at the many and
another gametophyte generation. This varied aspects ofbryophyte taxonomy and
basic cycle occurs in all three groups of ecology. Hopefully, this will be reflected
bryophytes but each group has its own in an increase in the publication rate of
variations; for example, most mosses have bryological papers in The Victorian
a filamentous stage of the gametophyte, Naturalist.
called the protonemal stage, which pro-
Fertilization
ofeggby
\
sperm Development of
sporophvtewhich
alwaysremains
attachedtothe
Gametophytcsproduce gametophyte
male and female
gametes, andmaybe
male, femaleor
i
bisexual
;
Sporesare
Protonemadevetop Sporesarereleased + producedwithin
thecapsuleby
budseachofwhich and germinaleto jf
meiosis
growinto a produceafilamentous
gametophyte gamexophytic stage,
theprotonema
Fig.5. Basicalternationofgenerationsinamoss.
194 The Victorian Naturalist
