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Nagi, J. Gaertner 1788

Nageia - Nagi description


Small to large evergreen trees, with trunk single and straight or variously forked and crooked in unfavorable habitats. Bark fibrous, peeling in flakes to present a mottled, smooth surface. Crown narrow, forming an irregular ball or cylinder constructed initially of horizontal tiers of branches densely or more openly clothed with foliage. Branchlets all elongate and bearing foliage leaves, without distinction into long and shoots, hairless, remaining green for at least the first year, more or less grooved between the very elongate attached leaf bases. Resting buds well developed, tightly wrapped by elongate green bud scales. Leaves evenly spaced along the twigs, in alternating pairs but aligned in two rows within a plane by twisting of the petioles and of the branchlets between the leaves, all leaves on one side of the twig facing up while those on the other face down as the twig lies flat, the members of a pair not always lined up perfectly across the twig. Individual leaves broad and multiveined, variably egg-shaped in outline, rather thick and leathery.

Plants monoecious. Pollen cones cylindrical, single or in clusters of up to seven at and near the end of a short, leafless stalk in the axil of a foliage leaf. Each cone with a few alternating pairs of sterile scales at the base and with numerous, densely crowded pollen scales. Each scale bearing two pollen sacs that are large compared to the somewhat heart-shaped blade. Pollen grains medium to large (body 40-45 µm long, 65-75 µm overall), with two kidney-shaped air bladders that are about the same size as or a little smaller than the oval, minutely bumpy body, the bladders with coarser squiggly ridges. Seed cones single or in clusters of two to five on short, branched or unbranched scaly stalks in the axils of foliage leaves, highly modified and reduced. Each cone with several alternating pairs of bracts on the cone axis, these either scaly and unmodified or (in two species) becoming united, fleshy, and swollen (the podocarpium). With a single, plump, unwinged seed embedded in an inverted position in each of one or two (or three) fleshy, green to black seed scales (the epimatium) in the axils of the uppermost bracts, maturing and falling in single season. Seeds nearly spherical, without a crest or beak. Cotyledons two, each with two veins. Chromosome base number x = 10 and 13.

Wood moderately hard and heavy, fragrant, decay resistant in soil and water, yellowish brown to gray, with a core of darker heartwood. Grain very fine and even, often with little distinction between early and latewood but sometimes with well-defined growth rings delimited by a narrow band of darker latewood. Resin canals absent.

Stomates numerous, forming many incomplete parallel lines either on both surfaces or just on the lower side. Each stomate sunken beneath and largely hidden by the four (to six) surrounding subsidiary cells, which support a well-developed, complete, nearly circular Florin ring that appears higher because it is surrounded by a depressed moat. Leaf cross section with one resin canal beneath each of the parallel veins, which are sometimes flanked by wedges of weakly developed transfusion tissue. Photosynthetic tissue either with a well-developed palisade layer on one side beneath the epidermis and adjacent hypodermis or with a more poorly developed palisade on both faces.

Five species in southern and eastern Asia and throughout Malesia, from southern and northeastern India (Kerala and Assam), the southern half of China, and southern Japan to the eastern tip of New Guinea.

Nageia (the name references the Japanese name for one of its species, nagi, Nageia nagi) is the only genus of Podocarpaceae with multiveined leaves, which resemble those of the unrelated kauris (Agathis, Araucariaceae) closely enough that the two may be confused, especially since some species of the two genera have overlapping distributions. Although the leaves of the two genera are both in pairs and are often similar in shape and texture, the veins in leaves of Nageia converge at the tip, while those of Agathis continue nearly parallel to the tip. The resting buds of leafy specimens also help to distinguish the two genera, since those of Nageia are pointy with narrow, pointed bud scales while those of Agathis are rounded with broad, rounded bud scales. Of course, if specimens are fertile, there is no possibility of confusion since the pollen cones of Agathis are much larger than those of Nageia while the seed cones of the kauris are typical conifer cones with numerous flattened seed scales bearing winged seeds. Since Nageia nagi has a long history of cultivation, selection for various morphological traits (including leaf shape and growth habit) has taken place, through few such cultivars are available outside of eastern Asia.

Nageia is closely related to Afrocarpus and Retrophyllum, as discussed under the latter, and beyond these two genera to Podocarpus, in which the Nageia species were long included. The closeness of these relationships, based on traditional characters as well as on DNA studies, makes it untenable to separate Nageia from these genera into a family of its own as has been proposed by some recent authors.

Other authors recognize more species in the genus than are accepted here, subdividing Nageia nagi into two to three species or more. The variability expressed by this species in cultivation makes it seem unwise to subdivide it without further study. There would, in fact, be something to be said for the opposite viewpoint of reducing the number of species accepted, with Nageia fleuryi and Nageia nagi on the one hand and Nageia motleyi and Nageia wallichiana on the other, differing in little but size of various parts. In the absence of additional evidence, the five species accepted here seem reasonably defensible. Likewise, attempts to apportion these few species between two botanical sections, based on the presence or absence of a swollen podocarpium, break down because of the intergradation of other characters, with Nageia maxima making a bridge between the two groups.

Unlike many other genera of podocarps (and conifers in general), there is no recognized fossil record of Nageia, so nothing is known of its Tertiary distribution and history. Some described broad-leaved podocarp fossils might belong to this genus but they are not well enough preserved for a definitive assessment of their affinities.




Attribution from: Conifers Garden