Araucariaceae

Araucariaceae – also known as araucarians – is a very ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods, when it was distributed almost worldwide.Most of the Araucariaceae in the Northern Hemisphere vanished in the Cretaceous–Paleogene extinction event, and they are now largely confined to the Southern Hemisphere, except for a few species of Agathis in Southeast Asia. Members of Araucariaceae are typically very tall evergreen trees, reaching heights of 60 m (200 ft) or more. They can also grow very large stem diameters; a New Zealand kauri tree (Agathis australis) named Tāne Mahuta ('The Lord of the Forest') has been measured at 45.2 m (148 ft) tall with a diameter at breast height of 491 cm (16.11 ft). Its total wood volume is calculated to be 516.7 m3 (18,250 cu ft), making it the third-largest conifer after Sequoia and Sequoiadendron (both from the Cupressaceae subfamily Sequoioideae). The trunks are columnar and have relatively large piths with resinous cortices. The branching is usually horizontal and tiered, arising regularly in whorls of three to seven branches or alternating in widely separated pairs. The leaves can be small, needle-like, and curved, or they can be large, broadly ovate, and flattened. They are spirally arranged, persistent, and usually have parallel venation. Like other conifers, they produce cones. Each tree can have both male and female cones (monoecious) or they can have only male or female cones (dioecious). Male cones are among the largest among all conifer cones, on average. They are cylindrical and drooping, somewhat resembling catkins. They are borne singly on the tips of branches or the axils of leaves. They contain numerous sporophylls arranged in whorls or spirals. Each has four to 20 elongated pollen sacs attached to the lower surface at one end. The pollen grains are round and do not possess wings or air sacs. Female cones are also very large. They are spherical to ovoid in shape and borne erect on thick, short shoots at branch tips. The numerous bracts and scales are either fused to each other or separate for half of their lengths. The scales almost always bear only one seed on its upper surface, in contrast to two in true pines (family Pinaceae). They are very large, among the largest seeds among conifers. They are dispersed by wind, usually using wing-like structures. On maturity, the female cones detach and fall to the ground. Due to their size, they can cause serious injuries if they hit a person. The cones of the bunya bunya, Araucaria bidwillii, for example, weigh 10 to 15 lb (4.5 to 6.8 kg), about the size and weight of a large pineapple. They can drop from heights of 23 m (75 ft). Araucariaceae is classified under the order Pinales, class Pinopsida of the division Pinophyta. The division includes all living conifers. Recently however, some authorities treat Araucariaceae as a separate order, Araucariales.