Conifers Garden US - World's conifers | Shipping Worldwide


Papuan incense cedar, H. L. Li  1953


Evergreen trees with fibrous, furrowed bark peeling in vertical strips. Crown open, broadly conical to flat-topped, with long, slender, gently upwardly arching branches well dispersed along the trunk. Branchlets in fernlike, flattened sprays, the predominantly paired branchlets arising only in the axils of lateral leaves. Resting buds unspecialized, consisting solely of embryonic and immature ordinary foliage leaves. Seedling leaves in alternating quartets, needlelike, flat, standing out from and somewhat crowded on the stem. Seedling phase short-lived, confined to the main axis during the first year of growth, with lateral branchlets bearing juvenile leaves appearing by the second year. Juvenile and adult leaves in alternating pairs, scalelike, dense, flat or bowed upward on the branchlets, the bases of lateral running down onto the branchlets and touching side to side except at the tip. Lateral and facial leaf pairs strongly distinct in juvenile foliage, becoming progressively less so with tree age, although still mostly quite distinct in maturity. Lateral leaves flattened side to side, more juvenile ones with large triangular tips standing out from the branchlet, later leaves with tips progressively reduced (except on main shoots) until the adult foliage with minute free tips. Facial leaves diamond-shaped and pressed against the twig, successive pairs completely separated by the bases of the lateral leaves, slightly to much smaller than the lateral leaves in juvenile foliage but less distinct from the smaller adult lateral leaves. Exposed lateral branchlets in the crown of mature canopy trees may be squarish rather than flattened in cross section and without obvious distinction between the facial and lateral leaf pairs.

Plants monoecious. Pollen cones crowded, but each single at the tip of a short branchlet, oblong, squarish in cross section. Each cone with 8-10 alternating pairs of pollen scales often arranged like four or five aligned quartets or so crowded as to appear irregular, each scale with two four pollen sacs. Pollen grains small (25-30 µm in diameter), spherical, minutely bumpy and sometimes with an ill-defined germination pore. Seed cones crowded but each single at the tip of a short branchlet, maturing in a single season. Each cone oblong, with two alternating pairs of thin, woody cone scales. Each scale with the bract portion fused to the seed-bearing portion and ending in a blunt tip near the bottom of the scale, the upper pair of scales fertile, about twice as long as the sterile lower pair. Each fertile scale with two seeds. Seeds oblong, with two very unequal wings developed from the seed coat in the upper half, the outer wing a mere fringe, the inner expanded over the far half of the seed scale. Cotyledons two, each with one vein. Chromosome base number not reported but probably x = 11.

Wood fragrant, light and soft, with whitish brown sapwood somewhat contrasting with the darker heartwood. Grain very even and moderately coarse, essentially without growth rings or these weakly marked by a few, irregular, slightly smaller latewood tracheids. Resin canals absent but with a few individual resin parenchyma cells scattered through the wood.

Stomates in lines and patches of varying density and extent on all leaf faces, the patches on the lower sides of the branchlets often whitened with wax. Each stomate sunken well beneath the four to six (or seven) surrounding subsidiary cells, which are commonly shared between adjacent stomates and topped by a nearly continuous Florin ring but do not generally bear additional papillae. Leaf cross section with a single-stranded midvein inside (morphologically above) and pressed against a large resin canal in the lower part of the leaf, both embedded in a cylinder of transfusion tissue. With up to eight additional resin canals (or none) spaced evenly around the whole periphery. Photosynthetic tissue forming a prominent palisade layer beneath the epidermis and adjacent thick but incomplete hypodermis over the whole leaf surface only on the upper face of the branchlet. Only one of each pair of facial leaves with a palisade layer while the other has spongy mesophyll extending all the way to the surface. Lateral leaves with palisade tissue on either the right or left side (the opposite ones for the two members of a pair) of these laterally flattened leaves rather than the evolutionarily upper (inner) side, which remains attached to the branchlet.

One species in New –Guinea and the Moluccas. Papuacedrus is the most northerly of the southern incense cedars (which also include Austrocedrus and Libocedrus), barely crossing the equator. It differs from the related genera in a number of small characteristics but most obviously in the very large juvenile lateral leaves, the distinctive shape of the adult lateral leaves, and in the position of the stout bract tip in the lower half of the seed scale rather than near the middle (as in Libocedrus) or near the end (as in Austrocedrus). Although these differences are small, information from DNA structures agrees with the separation of Papuacedrus from similar genera. A with many other tropical montane conifer genera, Papuacedrus papuana is not in cultivation, except in some botanical collections, and no cultivar selection has taken place.

Recognition of three distinct genera is also supported by the presence of fossils of all three in the Tertiary of Tasmania. Fossilized shoots of Papuacedrus have been recorded from Oligocene sediments (about 30 million years old) at two sites in Tasmania. These are the only known fossils of the genus.




Attribution from: Conifers Garden