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Introduction: Macrozamia plurinervia
is a small
(Section Parazamia
) cycad that is endemic to New South Wales.
It has a subterranean caudex and normally has a multi-twisted rachis.
History: Following a revision of L. A. S. Johnsons 1959
separation of
Macrozamia pauli-guilielmi
into three sub-species, M. plurinervia
(previously M. pauli-guilielmi
ssp. plurinervia
) was recognised as a
separate and distinct species by David Jones in 1991.
It was named after its many nerves and veins.
Distribution Range: M. plurinervia
has
a restricted distribution range in northern New South Wales and grows in and
around the area between Inverell and Tenterfield.
Habitat Conditions: M. plurinervia
usually
has an unbranched caudex and grows under a eucalypt canopy in a pattern of small colonies
of scattered individual plants or small groups of plants. It grows on either rocky slopes
in poor gravely soil or in surrounding flatter areas in sandy soil. Near Inverell,
it can be found growing in sandy soil, in flat locations, with a Callitris
sp. understorey,
under a eucalypt canopy.
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Figure 1. M. plurinervia
frond detail - note twisting of rachis.
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Figure 2. M. plurinervia
- frond detail: note the vivid yellow colour of
the callouses and the upper surface of the rachis.
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Climatic Data: Inverell (elevation 584 metres) has
an annual average rainfall of 764 mms (spread over 86 rain days) with winter minimum and
summer maximum temperatures (reached at least once per week in July and January) of
-4.7 and 34.1°C. respectively. Frosts occur on an average of 56 days per year.
Rainfall Patterns: 60% of the annual rainfall at Inverell falls
during spring and summer. The percentage seasonal rainfall pattern is as follows:
Summer: 35%, Autumn: 21%, Winter: 19% and Spring: 25%.
Principal Characteristics: The principal characteristics of
M. plurinervia
are as follows:
- a normally unbranched subterranean caudex
- a multi-twisted, but more or less straight/erect rachis
- mid-green coloured fronds, which grow to a maximum length of 1.1 metres
- pinnae with a concave surface
- yellow or reddish callouses at the point where the pinnae joint the rachis
- seeds with reddish coloured flesh.
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Plants: New fronds are a distinctive light-green colour,
with yellow or reddish callouses at the point where the pinnae join the rachis. Near Inverell,
where featured plants were photographed, the callouses and upper surfaces of the rachises
were a vivid yellow colour.
As happens with some other New South Wales Section Parazamia
species, the new fronds and
the pinnae callouses undergo a colour transformation as they age, with the fronds turning
a mid-green colour and the callouses turning a creamy-white colour.
Fronds: M. plurinervia
normally has a maximum of
about 8 fronds, with the norm being in the 3 to 5 range. Plants with 1 or 2 fronds are,
however, not uncommon.
In similar manner to other species with multi-twisted rachises, the pinnae on
M. plurinervia
fronds appear to extend radially from the rachis
(like the branches of a tree) but, in fact, the rachis itself spirally twists
through a number of complete 360 degree revolutions.
The pinnae extend more or less laterally from the rachis at an angle,
although they are normally angled slightly upwards,
with the apical pinnae extending at an extremely acute angle.
The number of complete twists of the rachis normally averages 3 to 4, sometimes more,
with the majority of these twists usually occurring in the upper section of the rachis.
The rachises on some mature plants, however, are only marginally twisted.
Likewise, the rachises on some small adult plants often twist gradually
through one only complete revolution.
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Figure 3. M. plurinervia
frond in habitat.
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Figure 4. M. plurinervia
in habitat.
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Cones: Cones are usually solitary,
but female plants can have 2 cones and male plants can have up to 3 cones.
Coning occurs on an irregular basis.
Affinities: There are four Section Parazamia
species
in New South Wales that have predominantly spirally-twisted rachises,
these are
M. concinna
,
M. fawcettii
, M. flexuosa
and M. plurinervia
.
On an affinity basis, M. plurinervia
is closely related to M. fawcettii
and to a lesser degree to M. flexuosa
.
Both
M. fawcettii
and M. plurinervia
are more robust than M. flexuosa
.
In addition, M. fawcettii
and M. plurinervia
have broader petioles and rachises,
and, also, broader pinnae, than M. flexuosa
.
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Figure 5. M. plurinervia
in habitat.
Figure 6. M. plurinervia
in habitat.
Figure 7. M. plurinervia
in habitat, with one (or possibly 2) infertile female cone(s).
Figure 8. M. plurinervia
top view of frond.
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Figure 9. Part of road washed away (on the way to the cycad location).
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Figure 10. Crooked bridge (on the way to the cycad location).
| Contributed by:
| Craig Thompson and Paul Kennedy (Text & Figures1-10)
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