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Huon pine, (Hook.f.) Quinn 1982

Lagarostrobos - Huon pine description


Evergreen trees and shrubs. Trunk cylindrical or fluted, dividing near the ground or free of major limbs for a third or more of its height. Bark obscurely fibrous, thin, smooth at first, later flaking in overlapping scales. Crown fairly open to dense, conical to irregularly and narrowly dome-shaped, with nearly horizontal to strongly upwardly angled branches. Branchlets all elongate, without distinction into long and short shoots, hairless, grooved between the attached leaf bases and remaining green for at least the first year (juvenile foliage) or completely hidden (adult foliage). Resting buds indistinct, consisting solely of as yet unexpanded ordinary foliage leaves. Leaves spirally attached. Juvenile foliage only moderately distinct from and giving way gradually but fairly quickly to adult foliage. Juvenile leaves scalelike, roundly triangular, a little flattened top to bottom, standing out from the twigs at a forward angle. Adult leaves scalelike, tightly pressed against and completely covering the twigs, overlapping, the exposed portion unevenly diamond-shaped, roundly to sharply keeled, with a toothed marginal frill.

Plants dioecious (a few individuals monoecious). Pollen cones single at the tips of otherwise ordinary short foliage shoots. Each pollen cone cylindrical, with a few bracts at the base and with 10-16 spirally arranged, triangular pollen scales, each with two pollen sacs. Pollen grains small to medium (body 20-40 µm long, overall 45-60 µm), with two relatively inconspicuously internally wrinkled air bladders that are much smaller than and mostly tucked under the very slightly elongate, minutely bumpy body, and accompanied by a prominent, small boss jutting out at the junction of the bladders with the cap of the body. Seed cones single and bent downward at the tip of otherwise ordinary foliage shoots, highly modified and reduced, with about 6-14 loosely spirally arranged bracts that become somewhat fleshy but do not unite into a podocarpium, maturing in a single season. Middle 4-8(-10) bracts fertile, from which one to five (to seven) seeds mature. Each fertile bract bears one seed that is nestled in the thin, papery, asymmetrically cup-shaped seed scale (the epimatium) and that has its opening pointed forward along the cone axis. Seed without an aril, hard, egg-shaped and somewhat flattened, wrinkled, ending in a broad, dimpled, straight beak. Cotyledons two, each with two veins. Chromosome base number x = 15.

Wood moderately soft and light, extremely durable, sweetly fragrant, the very pale sapwood sharply contrasting with the light brown to yellowish brown heartwood that is sometimes dotted with black. Grain very fine and even, with clear growth rings set off by a fairy broad band of slightly darker latewood. Resin canals and individual resin parenchyma cells both absent.

Stomates in patches on both sides but not arranged in lines or in any one direction. Each stomate sunken, plugged with wax that is not walled in by a Florin ring. Midvein single, inconspicuously buried in the leaf tissue of the adult leaves, with one resin canal immediately beneath it. Photosynthetic tissue forming a palisade layer on both sides of the leaf, without an intervening hypodermis inside the epidermis.

One species in Tasmania, Australia. Huon pine (Lagarostrobos franklinii), the sole living species of Lagarostrobos (the name, Greek for “slack cone”, reflects the droopy seed cone and its relatively widely spaced bracts), was once included in Dacrydium but is only distantly related to the species in that genus. Instead, Lagarostrobos is closely related to Manoao of New Zealand and to Parasitaxus of New Caledonia but differs enough to justify the maintenance of a separate genus. Although Lagarostrobos franklinii is cultivated to a limited extent in botanical gardens and arboreta, it is not in general cultivation, and there has been little cultivar selection, with the exception of one particularly weeping form.

Acceptance of Lagarostrobos as a segregate genus seems especially apt since it has been recognizable since the mid-Cretaceous, some 90 million years ago. These early records are pollen grains that closely resemble those of Huon pine, which is the only living conifer with a tubercle sticking out at the base of each air bladder. These pollen grains are from sediments widely distributed across the southern hemisphere, including southern Australia, New Zealand, southern South America, and parts of Antarctica. Everywhere they occur, the sediments and associated species indicate a wet habitat like that inhabited today by Huon pine. This pollen became progressively less common in mainland Australia during the early Tertiary as the continent dried, and it disappeared completely there after the Miocene, some 5 million years ago or more. Two other similar types of tubercle-bearing pollen grains are known from late Cretaceous and lower Tertiary sediments of the southern hemisphere, and these may well represent now extinct lineages of Lagarostrobos.

In contrast to the widespread and long-lasting distribution of pollen grains probably belonging to Lagarostrobos, the only known or recognized macrofossils attributed to Lagarostrobos are found in its present home, Tasmania. The oldest shoots are found in Oligocene sediments (about 30 million years old), while recognizable macrofossils of the living Huon pine, are first known from the early Pleistocene (less than 2 million years ago), a striking contrast to the long presumed pollen record of this species (or a very close relative).




Attribution from: Conifers Garden