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1 April 2011

An Araucaria tree

Figure 1: A photograph of an Araucaria tree taken in Carthage.

It is a relatively common sight to see Araucaria trees in Tunis, growing on public land as well as in private gardens.  "Araucaria is a genus of evergreen coniferous trees in the family Araucariaceae. There are 19 species in the genus, with a highly disjunct distribution in New Caledonia (where 13 species are endemic), Norfolk Island, eastern Australia, New Guinea, Argentina, Chile, and southern Brazil.


Description
Araucaria are mainly large trees reaching a height of 30–80 m. The horizontal, spreading branches grow in whorls and are covered with leathery or needle-like leaves. In some species, the leaves are narrow awl-shaped and lanceolate, barely overlapping each other, in others they are broad and flat, and overlap broadly.

 
The trees are mostly dioecious, with male and female cones found on separate trees, though occasional individuals are monoecious or change sex with time. The female cones, usually high on the top of the tree, are globose, and vary in size between species from 7–25 cm diameter. They contain 80-200 large, edible seeds, similar to pine nuts though larger. The male cones are smaller, 4–10 cm long, and narrow to broad cylindrical, 1.5–5 cm broad


Distribution
Many if not all current populations are relicts, and of restricted distribution. They are found in forest and maquis shrubland, with an affinity for exposed sites. These columnar trees are living fossils, dating back to early in the Mesozoic age. Fossil records show that the genus also formerly occurred in the northern hemisphere until the end of the Cretaceous period. By far the greatest diversity exists in New Caledonia, due to the island's long isolation and stability."
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