by Brian Johnston (Canada)
How fortunate we are that modern
commercial greenhouses have made the unique flora of Australia
available worldwide. The curved shapes of the unopened flowers of
this strange plant are thought to resemble kangaroo paws. Native
to the eucalyptus forests of Western Australia, modern hybridization
techniques have produced many alternative forms, some of which are sold
as long-lasting cut flowers. One such branch was the subject of
the present article.
The close-up above shows one of the
strange adaptations of this plant – its coating of fine wooly
hairs. It’s thought that the hairs make the plant taste strange
to predators, and discourage them from eating the flowers, leaves and
stems. The hairs also help to retain water in dry environments.
Kangaroo paws belong to the Haemodoraceae family, which is
related to the lilies. The genus name Anigozanthos is
thought to derive from the Greek “anises”
unequal and “anthos”, meaning flower. This refers to the
flower’s being divided into six unequal parts.
The two images that follow show a
typical group of kangaroo paw buds, several of which have begun to
open. The flower group shown is about ten centimetres high.
Notice the densely packed red hairs
on the surface of the plant’s stem. The darker green stem shown
at left is from the base of the plant, while the lighter green one at
right is a flower stalk. If you look carefully, you can see that
each hair has many barbs on its surface!
Several buds can be seen
below. In the left image, notice that every surface is covered
with a dense carpet of hairs.
The short stalks that connect the
buds to the main stem can be seen below. Notice that the red
hairs are concentrated in a ring around the base of each unopened
A bud has a base coating of pale
yellow-green hairs. Under the microscope, these hairs are seen to
be barbed from base to tip. Although the sharp barbs appear
lethal, the hairs are so fine and flexible that the surface feels downy
soft to the touch.
Two macro-photographs of the base
of a bud are shown below. Even without the aid of a microscope,
the barbed nature of the longer red hairs is evident.
By contrast, here are the same
hairs seen with the microscope. The entangled barbs form a loose
mat over the surface.
Three more images follow showing
this unusual defensive adaptation.
As a bud begins to bloom, the
narrow pointed wedges that form its tip separate to reveal the enclosed
reproductive structures. Note that the large unopened bud has
just begun to show the distinctive lines where the separations will
The interior of the mouth of a
flower is shown below. Six light brown anthers (male pollen producing
organs) are held in place by light green filaments. Projecting further
out than the anthers is the darker green pistil (the female reproductive
Five of the six petals have been
removed to show these structures more clearly. Notice that the
pistil is composed of a yellow-orange stigma
(pollen accepting organ), supported on the end of a long green style.
Under the microscope, the mature
stigma is red in colour. Note the pollen catching protuberances
that cover both the top of the style, and the stigma itself.
At the base of the flower, where it
attaches to the stalk, the style connects to a spherical, light green ovary (seed producing organ).
The anthers are connected by their
filaments not to the base of the flower, but to the base of each petal
lobe. This point of connection can be seen clearly in the image
that follows. Note that only the lobe itself is shown. The
tubular base (corolla) of the flower is below the area shown.
(The pistil has been removed for the photograph.)
Each anther appears to be composed
of two mirror-image sections. The particles covering the anther’s
surface are pollen grains.
Photomicrographs follow that show
the surface of an anther. Note the matted ribbons of tissue that
can be seen in the middle of each section of the anther.
The final sequence, with increasing
magnification, reveals the back of a cluster of kangaroo paw
buds. How different this plant is from the “typical” Canadian
Although kangaroo paw flowers can
be pollinated by small nectar-feeding marsupials, it is the birds that
do most of the work of fertilization. As a hummingbird sticks its
long beak down the flower’s tubular corolla to obtain the nectar at its
base, the head of the bird contacts both anthers and stigma.
Cross-fertilization occurs when the bird visits another plant, and
contacts the stigma with its pollen covered head.
Most of the macro-photographs were
taken with an eight megapixel Canon 20D DSLR equipped with a Canon EF
100 mm f 2.8 Macro lens which focuses to 1:1. A Canon 250D
achromatic close-up lens was used to obtain higher magnifications in
A few photographs were taken with
an eight megapixel Sony CyberShot DSC-F 828 equipped with achromatic
close-up lenses (Canon 250D, Nikon 5T, 6T, Sony VCL-M3358, and shorter
focal length achromat) used singly or in combination. The lenses screw
into the 58 mm filter threads of the camera lens.
The photomicrographs were taken
with a Leitz SM-Pol microscope (using a dark ground condenser), and the
A Flower Garden of
A complete graphical index of all
of my flower articles can be found here.
The Colourful World of
A complete graphical index of all
of my crystal articles can be found here.
Microscopy UK or their contributors.
Published in the March
2010 edition of Micscape.
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