Araucariaceae

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Araucariaceae

Description

Monoecious, medium-sized to very large trees (rarely shrubby in very exposed situations). The leaves vary from scales or needles to broad leathery forms with many parallel veins sometimes on the same plant at different stages of growth. Seeds produced in large, well-formed cones which disintegrate when mature, dispensing the seeds in most cases with the help of wing-like structures;

Distribution

Antarctic: present Asia-Tropical: Australasia: New Caledonia: present New Zealand: present Pacific:, Fiji (Fijipresent) South America: present cooler parts of South America: present
The 40 species in two genera are well represented in Malesia (13 spp.) and extend eastward and southward into Fiji, New Caledonia (18 spp.), Australia, and New Zealand, with 2 spp. also in the cooler parts of South America, giving the family a distinct Antarctic relationship. Only one species of Araucaria (in South America) occurs completely outside of the tropics, while the majority of the species in the family belong in the lowland tropics and others grow in the tropical highlands.

Taxonomy

Two well marked genera are recognized.

Uses

The large size of individuals in many species in this family along with the excellent quality of the wood has made them prime candidates for lumber production where sufficiently dense stands occur. The wood is light coloured, yellowish or brownish, straight grained, easily worked, durable, and generally similar to pine but somewhat harder than the more familiar types. The wood is sometimes intermingled and hardly distinguishable from material of Podocarpaceae. Important stands of A gathis have been exploited in Borneo and stands of Araucaria in New Guinea (ISMAIL, 1964; GRAY, 1975; HAVEL, 1971), as well as many locations outside of Malesia. Heavy exploitation has reduced the economic importance of this family. Some attempts have been made to establish tree plantations, but this effort is in the early stages of development (WHITMORE, 1977, 1980; BOWEN& WHITMORE, 1980). Large quantities of pitch have been gathered, particularly from certain species of Agathis where it is known as 'dammar'. Both fossil pitch with darker colours and fresh pitch which is much lighter have been produced. Immense dammar trees sometimes have some form of steps built into their trunks to enable collectors to reach the accumulating pitch. Specimens of various species make handsome ornamentals and are widely used in landscaping in the warmer parts of the world. (The seeds of several Araucaria species are in great demand as food.)

Notes

The great size of trees in this family has led to an emphasis on collection of juvenile foliage specimens and immature cones and when this is not admitted by the collectors the result can be misleading. Because the seed cones shatter on maturity and the pollen cones are deciduous, it is next to impossible to collect attached mature fertile material. Fallen cone scales and pollen cones abound below mature trees and should be collected.

Embryology

The fertilized egg undergoes at least five mitoses resulting in 32 or more free nuclei before cell walls form. The resulting cluster of cells deep inside the egg (proembryo) is then organized into three parts. The cells closest to the archaegonium elongate to form a massive 'pro-suspensor' while those on the opposite side form a temporary 'cap'. The cells at the centre of the proembryo become the embryo proper, which does not undergo cleavage as in many other conifers. Simple polyembryony resulting from more than one fertilized archaegonium, however, may occur. The large number of proembryo cells and the massive embryonic 'cap' are distinct for Araucariaceae within the conifers. The chromosome number is n= 13. No hybridization is suspected.