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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” meaning 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 flower.

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 occur.

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 organ).

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 garden flower!

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.

Photographic Equipment

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 several images.

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 Coolpix 4500.

A Flower Garden of Macroscopic Delights

A complete graphical index of all of my flower articles can be found here.

The Colourful World of Chemical Crystals

A complete graphical index of all of my crystal articles can be found here.

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© Microscopy UK or their contributors.

Microscopy UK Front Page
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