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Cathaya, W. Y. Chun & Kuang 1962

Cathaya description


Evergreen trees with a straight, single trunk bearing horizontal branches. Bark nonfibrous, smooth at first, becoming flaky and then furrowed. Crown conical in youth, gradually flattening and becoming dome-shaped with age. Shoots weakly differentiated into two kinds. Sterile side shoots shortened and with needles concentrated at the tips, but not long-lived like those of Larix and Cedrus. Long main shoots with seasonally varying spacing between leaves, the more condensed sections with the needles in pseudowhorls like those of the short shoots. Twigs shallowly ridged and furrowed, completely clothed by the woody, persistent, leaf bases. Leaf attachment scars round or squarish, flush with the ridges or raised on a low peg. Winter buds well developed, with thin scales falling cleanly in spring, not resinous. Leaves closely or openly spiraled, needlelike, flat, straight or slightly curved to one side, gradually tapering to a short stalk.

Plants monoecious. Pollen cones single, with several sticking out from separate buds in the axils of needles at the tips of the previous year’s twigs. Pollen scales numerous, densely spiraled, each with two elongated pollen sacs attached to its stalk. Pollen grains medium to large (body 45-60 µm long, 55-75 µm overall), with two round air bladders a little smaller than the oblong body and covered with a more open, squiggly, minute sculpturing than the body. Seed cones single from buds in the axils of needles on twigs of the previous year, unstalked, upright at pollination but sticking straight out from the twigs at maturity, maturing in a single season but persisting several years. Seed scales round, spirally arranged, spreading at maturity to release the seeds. Bract attached to the seed scale only at the base, much smaller, triangular with a prolonged, pointed tip. Seeds two per scale, the body egg-shaped, the asymmetrical wing similar and larger in both length and width but much smaller than the seed scale and derived from it, cupping the seed body from below. Cotyledons three or four, each with one vein. Chromosome base number x = 12.

Wood similar to that of Pseudotsuga in the distinctive, spirally thickened water-conducting cells (tracheids) but differing in the more prominent growth rings formed by a more gradual transition from early- to latewood. Vertical resin ducts confined to the latewood and earlywood-latewood transition.

Stomates arranged in two broad bands beneath, one on either side of the midrib, each band consisting of 10-20 lines of stomates. Individual stomates sunken beneath and tucked in under the four to six subsidiary cells, which are topped by a stout Florin ring. Leaf cross section with transfusion tissue right beneath the single-stranded midvein and two resin canals, one on each side out toward the leaf margin just inside the lower epidermis at the outer edge of the stomatal band. Photosynthetic tissue without a palisade layer but with a somewhat radial organization of the part of the spongy mesophyll that lies beneath the upper leaf epidermis and adjoining discontinuous to continuous thin hypodermis.

One species in China. The affinities of Cathaya (the name honors its country of origin, since Cathay is a historical name for China) are controversial and apper to vary with the kind of evidence examined. Most features favor an alliance with Pseudotsuga and Larix, but DNA studies suggest a closer, albeit still distant, relationship with Pinus and Picea. Despite placement of the sole species in Tsuga by some authors, there are no important similarities with this genus or any other genus in the abietoid subfamily of the Pinaceae. Although cultivated in botanical gardens in China, Cathaya argyrophylla is scarcely known outside of its homeland, and no cultivar selection has taken place. Cathaya has a sparse fossil record across Eurasia, consisting mostly of pollen grains as early as the late Oligocene, about 25 million years ago, and it has also been reported from shoots, cones, and seeds in Miocene sediments of Idaho.




Attribution from: Conifers Garden