Japanese cedar, D. Don 1839
Cupressaceae

Cryptomeria - Japanese cedar description

Evergreen trees with a single, straight, often massive trunk or forming clonal clusters. Bark fibrous, shallowly furrowed and peeling in vertical strips on narrow ridges. Moderately densely branched, the lower branches, if persistent, capable of rooting and turning up to form subsidiary trunks, although the stumps cannot resprout. Without specialized winter buds. Leaves densely spirally arranged, sticking out all around the twig, claw-shaped (to scalelike) in adults but longer and straighter in young trees, the bases running down on and completely clothing the twigs. Free portion flattened side to side and more or less diamond-shaped in cross section, tapering gradually to a soft, slightly incurved point.

Plants monoecious. Pollen cones clustered near the tips of the twigs but each single in the axil of a foliage leaf, oblong, with about 20 spirally arranged pollen scales. Each scale with a thin stalk and a rounded, triangular blade bearing three to five pollen sacs at its base. Pollen grains small (25-35 µm in diameter), nearly spherical, with a small, nearly straight, smooth germination papilla, the rest of the surface covered with minute bumps. Seed cones single at the tips of twigs, maturing in a single season, woody, nearly spherical but slightly pointed. Cone with 20-30 spirally arranged seed scales, the upper- and lowermost of which are sterile. Seed scales more or less wedge-shaped, the bract portion a little shorter than the fertile portion and fused to it for most of its length, the exposed part triangular and coming to a sharp point. Fertile portion consisting of four or five pointed lobes fused side to side at their bases (hence the scientific name, Greek for “hidden parts”), with three to five (or six) seeds. Seeds oblong, slightly flattened, with two very narrow wings derived from the seed coat. Cotyledons (two or) three, each with one vein. Chromosome base number x = 11.

Wood faintly fragrant, very soft, weak, and light but moderately decay resistant, with pale yellowish brown to pinkish brown sapwood gradually changing to a dark reddish brown heartwood. Grain moderately even and variably fine to fairly coarse, with sharply defined growth rings marked by a gradual transition to a broad band of much smaller and thicker-walled latewood tracheids. Resin canals absent but with individual resin parenchyma cells scattered through the growth increment and often somewhat concentrated into relatively narrow bands, especially in the latewood.

Stomates arranged in broad but relatively inconspicuous bands on each face. Each stomate oblique to the long axis of the bands, sunken slightly beneath the four to six subsidiary cells and not surrounded by a Florin ring, although there may be an inconspicuous trough around the subsidiary cells. Leaf cross section with a nearly central single-stranded midvein flanked by patches of transfusion tissue and paralleled beneath by a slender resin canal. Epidermis underlain all the way around (except under the stomatal lines) by a hypodermis. Photosynthetic tissue with a multilayered palisade occupying most of the upper portion above the midvein and a looser spongy mesophyll throughout the remainder.

One species in eastern Asia. Cryptomeria japonica is most extensively and intensively cultivated in Japan although it is widespread in botanical gardens and specialty collections elsewhere and enjoys modest general popularity. There has been extensive cultivar selection in Japan, involving growth habit (with many dwarfs of varying shape) and foliage characteristics, such as needle length and color and branching habit, including a dramatic cockscomb-bearing cristate cultivar. The most popular cultivar outside of Japan, however, is probably the permanently juvenile-foliaged Cryptomeria japonica ‘Elegans’, which also has a striking reddish bronze winter coloration.

Cryptomeria occupies an ambiguous position within the family Cupressaceae. One of the genera formerly separated into the family Taxodiaceae (or even its own monotypic family Cryptomeriaceae), it has shoot and cone structures reminiscent of those of some of the most ancient modern conifers, the so-called transition conifers. It has been compared especially to the late Permian genus Pseudovoltzia, which is one of the key genera in theoretical interpretations of the compound nature of conifer seed cones.

Most evidence suggests a closest relationship to Glyptostrobus and Taxodium, with Glyptostrobus showing many transitional characteristics between the two genera, negating the suggestion that Cryptomeria should be given its own family. The side-to-side seed-bearing teeth that make up the seed scale, so reminiscent of those of the extinct Pseudovoltzia, seem unique when examining mature cones of extant conifers. However, development studies of seed cones from their inception show that this kind of structure also underlies the more fused seed scales of the closely related Glyptostrobus and Taxodium as well as the less closely related Cunninghamia and even the more distant Sciadopitys, the only living member of the related family Sciadoptyaceae. Thus seed cone structure, which seems anomalous at first blush, reinforces the close relationship of Cryptomeria to Glyptostrobus and Taxodium, uniting them into their own botanical tribe (Taxodieae) within the Cupressaceae.

Unlike these closest relatives and the more distantly related Metasequoia and Sequoia, however, Cryptomeria does not seem to have been a widespread, dominant member of northern hemisphere forests during the Tertiary. In fact, there are very few secure records of fossil Cryptomeria outside of Japan. Despite its similarities to the transition conifers, its confirmed fossil record extends back no earlier than the beginning of the Tertiary, far less than that of Cunninghamia-like conifers, the oldest modern members of the family.

References

• Farjon, A. (2010). A Handbook of the World's Conifers. Koninklijke Brill, Leiden.
• Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland.
• IUCN Red List of Threatened Species, International Union for Conservation of Nature and Natural Resources. Cambridge, UK /Gland, Switzerland

Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.