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Keteleeria, Carrière 1866

Keteleeria description


Evergreen trees with a straight, single trunk bearing irregular tiers of rising to horizontal branches to form a conical crown when young, generally becoming broad and domelike or flat with maturity. Bark not fibrous, grayish brown and smooth at first, darkening and becoming flaky with age and then ridged and furrowed at the base of mature trunks. Branchlets all elongate, without distinction into long and short shoots, hairy or not, grooved between raised leaf bases bearing a lightly raised leaf attachment. Winter buds well developed, scaly, the scales remaining on the twigs for several years. Leaves spirally arranged, sometimes radiating all around the twigs but more commonly sticking straight out to the sides and sometimes above as well. Each leaf needlelike, flat, generally sword-shaped, usually straight or slightly curved, long pointed in juvenile foliage and on sprouts, bluntly pointed, rounded, or shallowly notched in adult foliage, tapering to a short petiole.

Plants monoecious. Pollen cones in rings of 4-10 from single buds at or near the tips of shoots, each on a short, slender stalk and with numerous, spirally arranged pollen scales, each bearing two pollen sacs. Pollen grains large to very large (body 55-125 µm long, some the largest among all living conifers), with two round air bladders that have a relatively small area of attachment to the large, oval, minutely bumpy body, the bladders with more wrinkled sculpturing. Seed cones cylindrical or slightly egg-shaped, single at the tips of ordinary, stout branchlets, upright both at pollination and at maturity, maturing in a single season and then releasing the seeds, but remaining on the tree and gradually breaking up in place or breaking off above the bottom scales, with numerous, densely spirally arranged, woody, thin seed scales. Seed scales of various shapes from circular to triangular but always with a thin stalk flanked by two small, downwardly directed lobes. The bract roughly half as long as but often not visible between the scales in the intact mature cone, with a three-lobed blade at the end of a longer (or nearly equal), stalk united with the stalk of the seed scale. Seeds two per scale, wedge-shaped, the asymmetrical wing derived from the seed scale and as long as it, cupping the seed body loosely on one side and wrapping around to cover about one quarter to one third of the other side. Free part of wing twice as wide as the body and about two to three times as long. Cotyledons two to four, each with one vein, remaining within the seed coat underground. Chromosome base number x = 11.

Wood soft, slightly fragrant, light brown with a distinct reddish brown heartwood. Annual rings well developed and with abundant latewood. Vertical resin canals often present, especially in response to injury, but resin ducts absent from the rays.

Stomates arranged in two waxy or dark green bands beneath and sometimes also with a few to many incomplete lines above. Each stomate sunken deep in a pit beneath the four (or five) neatly arranged subsidiary cells that are covered with a very thick cuticle but are not circled by a further thickened Florin ring. Leaf cross section with a single-stranded midvein above a strand of transfusion tissue and with a resin canal on either side inside the lower epidermis near the needle edge. Photosynthetic tissue with a well-defined single palisade layer beneath the upper epidermis and adjacent, nearly continuous (except beneath lines of stomates, when present) hypodermis, the remainder consisting of spongy mesophyll connecting the palisade to the stomatal bands beneath.

Three species in China and Indochina. Tree of Keteleeria occur at generally lower elevations and in dried habitats than the true firs (Abies) and spruce (Picea) occupying the same general region. The name honors Jean-Baptiste Keteleer (1813-1903), a Belgian horticulturist and nurseryman. Both species remain relatively uncommon in cultivation although Keteleeria davidiana, more widespread in nature, is also more frequently encountered in collections. Consequently, there has been no cultivar selection.

Although most closely related to Abies, as evidenced by general morphology, immunological reactions, and DNA studies, Keteleeria has more in common with some pine (Pinus) species ecologically and in its wide-crowned growth habit. The species were originally confused with Abies but were recognized as a distinct genus within 20 years of their introduction to Europe. They differ from Abies most obviously in their clustered pollen cones and the fact that their seed cones do not break up with maturity.

Like Douglas firs (Pseudotsuga), the two species of Keteleeria vary greatly in seed cone characteristics: the length and width of the whole cone, the shape of the seed scales and attached bracts, and the corresponding shape of the seed wing. The needles also vary with age of the tree and with climatic conditions. As a result, some 16 species and a few additional varieties were named, several in the period 1975-1983. The treatment in the Flora of China (Fu et al. 1999c) accepted five species and four additional varieties, while Farjon (1989), in a detailed revision of the genus, accepted the three species commonly recognized before Flous’s (1936) revision. Little is known about the range of variation in natural populations of Keteleeria. Progress in understanding the taxonomic structure of the genus, however, will depend on detailed population studies rather than the limited available herbarium material. Unfortunately, many populations were decimated by forest clearance if not by specific exploitation.

Fossils of Keteleeria are known from Oligocene deposits more than 23 million years old in both Europe and western North America. The genus disappeared from North America before the close of the Miocene (more than 5 million years ago) but lasted into the succeeding Pliocene in Europe, by which time there are records of the genus in Asia as well.




Attribution from: Conifers Garden