Taiwania, Hayata  1906
Cupressaceae

Taiwania description

Evergreen trees with single, straight, fluted trunk clothed with thick, fibrous, red-brown bark peeling in strips. Crown shallow and open, composed of slender to moderately thick, gently upwardly angled branches. Branchlets very weakly differentiated into short-lived short shoots and long shoots that persist as the main branching framework. Short shoots shed intact, completely clothed by the persistent leaf bases, drooping gracefully from the horizontal branches, especially in young trees. Resting buds without specialized bud scales, formed solely by the normal spiral of variously immature ordinary foliage leaves surrounding the shoot apex. Leaves densely spirally arranged, of three types. Seedling leaves needlelike, flattened top to bottom with a prominent midrib beneath. Transitional juvenile leaves clawlike, flattened side to side and straight or slightly curved forward, progressively shorter with maturity of the tree. Adult leaves scalelike, diamond-shaped in cross section, curved forward and overlapping along the branch.

Plants monoecious. Pollen cones in radiating clusters of (one to) three to seven (to nine) from a common winter bud at the tips of branchlets. Pollen scales spirally arranged, 15-20, each with two or three pollen sacs. Pollen grains small (20-35 µm in diameter), spherical, with a small germination papilla but otherwise almost featureless. Seed cones single from winter buds at the tips of branchlets, more or less egg-shaped. Cone scales spirally arranged, 18-36, of which the middle 10-20 are fertile. Each scale thin and rounded, with an abruptly pointed tip, consisting mostly of the bract portion, with the fully fused seed-bearing portion reduced to a pad beneath the two seeds. Seeds lens-shaped, flattened, with an equal pair of wings derived from the seed coat, each wing longer than and about as wide as to a little wider than the body. Cotyledons two, each with one vein. Chromosome base number x = 11.

Wood odorless, light and soft but decay resistant, with nearly white sapwood sharply contrasting with the pale brown heartwood with purplish brown streaks. Grain very fine and even, with well-defined growth rings marked by a somewhat gradual and then abrupt transition to much smaller and noticeably thicker walled latewood tracheids. Resin canals absent but with sparse individual resin parenchyma cells scattered throughout the growth increment.

Stomates in waxy white bands on all four faces of both adult and juvenile leaves but not arranged in defined lines. Individual stomates sunken beneath and partially hidden by the innermost of one to three rings of four to six surrounding subsidiary cells. Leaf cross section with a nearly central single midvein right above a single more or less equal-sized resin canal and flanked by prominent wings of transfusion tissue. Photosynthetic tissue very weakly organized into a thin, incomplete palisade layer all around the leaf periphery inside the epidermis and incomplete single hypodermal layer, with the rest consisting of spongy mesophyll surrounding the midrib and associated tissues.

One species in western China and Taiwan. Taiwania is unusual among general of the Cupressaceae in its superficially sprucelike cones, which differ, however, in having a very reduced seed-bearing portion. In this, it somewhat resembles Cunninghamia and, to a lesser extent, Athrotaxis. The foliage has some resemblance to that of Cryptomeria and somewhat less to that of Sequoiadendron but differs considerably in detail. While thus sharing features with a variety of genera of Cupressaceae, it does not seem to be particularly closely related to any one of them, and this lack of close relationships is also reflected in DNA studies (Brunsfeld et al. 1994). Although a single species is a accepted here and in the Flora of China, many Chinese botanists, and a few elsewhere, have separated the mainland populations from those of Taiwan as distinct species. Although some material from continental Asia has larger cones and smaller leaves than the Taiwanese specimens, the difference appear minor, and there is too little material of the mainland trees to convincingly establish their full range of variation, so there appears to be little justification for distinguishing them. Taiwania cryptomerioides generally grows poorly in cultivation outside of its native range, and no cultivar selection has taken place.

Taiwania has a very sketchy fossil record with the oldest known specimens recorded in sediments of uncertain age (either late Paleocene or early Eocene), roughly 65 million years old, from Spitsbergen in the high arctic. From the Eocene, some 50 million years ago, into the Pliocene, some 4-5 million years ago, the genus was well established in Japan, but there is no fossil record from China.

Species:

Attribution from: Conifers Garden