Bald cypress, L. Richard  1810
Cupressaceae

Taxodium - Bald cypress description

Deciduous or subevergreen trees with a single, straight, buttressed trunk covered by fibrous, furrowed bark. Base of tree often surrounded by varying densities of cypress knees, which are more or less cone-shaped woody outgrowths from the roots, especially under swampy conditions. Densely branched from the base at first with upwardly arcing branches, the lower branches falling to leave a clear, straight bole. Shoot system moderately differentiated, with once-branched or unbranched deciduous (cladoptosic) determinate short shoots borne on permanent long shoots. Shoots emerging from definite winter buds. Leaves arranged spirally but often distichously spread out in one plane on either side of the twig by twisting of the petiole, standing out from the branchlets or tightly pressed forward along them, the attached leaf bases clothing the short shoots but less evident on long shoots. Leaves needle- to scalelike, predominantly of one form or the other in each species or variety, generally narrowly strap-shaped, except triangular when short, thin and soft, flattened. Autumn leaves turning from bright green to reddish brown, remaining attached to the short shoots and falling with them or shed individually on long shoots.

Plants monoecious. Pollen cones numerous, single and unstalked in the axils of scale leaves along dangling, branched, reproductive shoots. Individual pollen cones oblong, with 10-20 spirally arranged triangular pollen scales, each with 2-10 pollen sacs. Pollen grains small (25-35 µm in diameter), nearly spherical, with a small triangular germination papilla and minutely granular surface. Seed cones numerous, clustered but each single at the end of a short branchlet, maturing in a single season, remaining tightly closed until maturity and then disintegrating into individual scales and seeds, either in place or after being shed intact. Individual cones spherical to oblong, with 5-25 spirally arranged thin, peltate, resinous scales on thin stalks. Each cone scale with a roughly diamond-shaped bract tipped by a low, broadly conical boss on the face, fringed around the upper edge by rounded, toothlike lobes of the intimately fused seed scale and with (one or) two seeds. Seeds chunky, angular, wingless, resinous, readily floating in water. Cotyledons four to nine, each with one vein. Chromosome base number x = 11.

Wood commonly greasy and with a sour odor, occasionally dry and odorless, light to moderately heavy, soft, relatively strong and decay resistant, with pale yellowish white sapwood giving way gradually to the highly varied heartwood, ranging from yellowish or light brown through various reddish brown shades to almost black. Grain rather coarse and very even to somewhat uneven, with well-defined or somewhat irregular (because of partially missing or extra false) growth rings marked by a gradual or abrupt transition to a broad or narrow darker band of smaller, thicker-walled latewood tracheids. Resin canals absent but with numerous individual resin parenchyma cells scattered through the growth increment or loosely organized into open bands.

Stomates confined to two weakly distinguishable stomatal bands beneath or broadly distributed across both surfaces except over the midrib, only occasionally forming defined lines. Each irregularly oriented stomate sunken beneath and partially hidden by the four to six low surrounding subsidiary cells that entirely lack a Florin ring. Midvein single, often grooved above, and flat or slightly raised beneath, with or without a single resin canal immediately beneath it, and flanked by wedges of transfusion tissue. Photosynthetic tissue with a single palisade layer immediately beneath the upper epidermis without an intervening hypodermal layer, and with spongy mesophyll constituting the bulk of the tissue down to the lower epidermis.

Two species in southern North America. The generic name Taxodium (Greek for “yewlike”) reflects the fact that this was the first conifer genus (among what later became a flood of genera) encountered by European botanists with foliage more or less reminiscent of that of common yew (Taxus baccata), which is rather distinctive when considering only European conifers. Despite having been introduced to cultivation more than 250 years ago, very few bald cypress cultivars have been selected, and these have almost all been based on variations in growth habit: columnar, broad, slightly drooping, or dwarf.

The distinctive cypress knees, woody conical projections rising upward from the root system, are found only in species of Taxodium and Glyptostrobus growing in swampy soils. They are generally thought to be involved in aeration of the root system, but this has yet to be demonstrated decisively. The Asian Glyptostrobus and Cryptomeria are the closest living relatives of this now exclusively North American genus. The nine phylogenetically most basal genera of the family Cupressaceae were traditionally recognized as a separate family Taxodiaceae, of which Taxodium is the type genus. In phylogenetic terms, however, Taxodium, Glyptostrobus, and Cryptomeria are actually more closely related to the larger crown group of Cupressaceae that includes the junipers (Juniperus), cypresses (Cupressus), incense cedars (Libocedrus and others), and 16 other genera in both the northern and southern hemispheres than they are to the other six genera (including the redwoods: Sequoia, Sequoiadendron, and Metasequoia) included with them in the segregate Taxodiaceae.

The oldest known Taxodium fossils are found in late Cretaceous deposits of North America, dating to more than 65 million years ago. It was much more widespread around the northern hemisphere during the Tertiary and persisted in Europe into the Pliocene, perhaps as recently as 2.5 million years ago. The trees were particularly abundant in the now arid Columbia Plateau region of Oregon and Washington during the late Tertiary, when ashfalls from the emerging volcanoes of the Cascade Range dammed streams, creating many swamps.

Species:

Attribution from: Conifers Garden