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A street tree of Eucalyptus racemosa in Sydney

Eucalyptus racemosa commonly known as the narrow leaved scribbly gum or snappy gum, is a tree native to eastern Australia around Sydney. It grows in poor sandstone soils in mid to high rainfall areas.

The leaves and the stem

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The leaves are long and the length is about five to six times the width, 7 to 15 cm long, 1 to 2.5 cm wide, greyish green on both sides of the leaf.

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Leaf venation and oil glands in a fresh leaf viewed with transmitted light. The yellow white structure in the middle is the midrib.

The bark is smooth with shedding bark of white, grey or yellow. Scribbles often found on the bark. The scribbles were formed by certain insect attack leaving distinctive scribble marks.

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Smooth barked, with shedding bark of white, grey or yellow. Scribbles often found on the bark.
Scribbles in detail
Scribbles in detail

The flowers

The showy parts of the flowers are the white filaments of the stamens. Instead of having petals and sepals, a flower has an  hypanthium (base) in green colour and an operculum (lid) in white. (The hypanthium and operculum have similar origins as both petals and sepals combined.)

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The flowers and leaves in situ on the tree

 

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Flower buds and flowers in full bloom
A young flower bud. The whole protection including the operculum is green
A young flower bud. The operculum is green
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The operculum (lid) has turned white and becomes conspicuous

 

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A flower bud cut into two halves to show the stamens, green pistil and ovary inside

The operculum splits open to release the stamens. Stamens are male reproductive structures made up of anthers and filaments. The anthers produce pollen grains.

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Stamens with the yellow anthers at the tip are the conspicuous part of the flower

The female reproductive structure is called the pistil. It is made up of the stigma, style and ovary. The stigma receives pollen grains. The male nuclei of the pollen grains transferred through the tissue of the style into the ovary. The ovary comprises of 4 carpels. Each carpel contains numerous ovules.

The pistil of the flower. The top part is the stigma, the middle is the style and the bottom part is the ovary.
The pistil of the flower. The top part is the stigma followed by the style. The ovary is at the bottom.
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Transverse section of the ovary showing the four carpels with ovules inside, ie 4 locular ovary
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The ovules have been dislodged a little to show the three dimensional appearance.

 

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The longitudinal of the ovary of a flower bud showing the ovules inside.

 

The longitudinal section of the ovary of a mature flower
The longitudinal section of the ovary of a mature flower
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The ovules have been dislodged to show the three dimensional appearance.

The male nuclei fertilize the female nuclei in the ovule. The ovule develops into a seed. The ovary becomes a fruit (gum nut). The fruit is barrel-shaped, 4 locular, 4-5 mm long, 5-6 mm in diameter. It has 4 valves at rim-level.

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Fruits of flowers of the precious year
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A fruit of the flower of the previous year
The top view of a fruit
The top view of a fruit
The fruit cut open to show the 4 compartments inside
The fruit cut open to show the 4 compartments inside

 

Bibliography

http://www.hornsby.nsw.gov.au/media/documents/environment-and-waste/bushland-and-biodiversity/native-tree-database-fact-sheets/Fact-sheet-Eucalyptus-racemosa-Narrow-leaved-Scribbly-Gum.pdf

http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Eucalyptus~racemosa

 

 

 

 

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