Tên Khoa học: Camellia ligustrina Orel, Curry & Luu.
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Tên tiếng Việt: Trà mộc
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Perennial, small to medium evergreen shrub, 4-6 m high, with upright habit, well branched, almost always multi-stemmed; main stem to 25 cm thick at base; secondary branches thin and ascending at ca. 45°; mature bark generally smooth, rougher toward stem bases, with dull sheen, unevenly blotched, reddish to light cinnamon to light brown; new shoots thin, reddish purple to brown, finely tomentose, with short white hairs; older branches light gray and finely tomentose; mature branches glabrous, reddish to light cinnamon to light brown. Petioles short, 0.3-0.5 cm x 2(—3) mm, mostly linear, sometimes slightly falcate, slightly wider distally, finely tomentose, light to mid-brown abaxially, mid-green to brown adax- ially, with a light brown, shallow, longitudinal channel ca. 1 mm wide, <1 mm deep; dormant axillary leaf buds small, rudimentary, laterally compressed, sometimes slightly falcate, finely hairy, 1-3 X 1—1.5(—2) mm, dark brown; terminal leaf buds light to mid-green, later brown to dark brown, hairy, short and slightly flattened, with sharp apex, 0.8— 1(—1.3) X 3—4 mm, with scale margins also hairy; developing leaves light green, with distinct sheen, glabrous, narrowly elliptic to elliptic oval, distally regularly serrate, less so proximally; mature leaves narrowly elliptic to elliptic, distally regularly serrate, less so proximally, glabrous, to 8.5 X 2.5—3(—3.5) cm, with adaxial surface dark green, shiny, shallowly pitted, lighter green and almost dull below; leaf apex mostly cuspidate, sometimes acute; leaf base obtuse to acute; midrib shallowly sunken adaxially, <1 mm wide proximally, narrower distally, shortly and finely hairy, red-brown, more so proximally, prominent abaxially, proximally to 2 mm wide, <1 mm wide distally, light green, proximally hairy, with hairs long, orange-red; secondary venation pinnate, not distinct, sometimes so faint on adaxial surfaces as to be invisible, more prominent but still faint abaxially, mostly brochidodromous, sometimes not developed and appearing to be camptodromous, with 4 to 5(6) pairs of veins adaxially, the veins shallowly sunken, abaxially slightly prominent; tertiary venation lack­ing. Flowers sessile to almost sessile, terminal, solitary, sometimes in pairs, lacking scent; flower buds small, orbicular, densely tomentose, brownish green, but whitish green distally, with developing perules prominent; flowers 2.5-3.5 cm diam. (the relatively small flower size due to folding of mature petals), white, soft, thicker toward center; petals 5, partially twisted along their longitudinal axis, with apices unevenly folded to varying degree, arranged in 2 whorls, glabrous, sometimes frayed distally, not emarginate, overlapping proximally for 0.5-0.8 cm, lacking midrib, with venation absent; petals of outer whorl 2 or 3, (2-)2.5-3.5 X (0.5-)0.75-1.2 cm, slightly concave, sometimes asymmetric, narrowly elliptic to almost oblong, proximally slightly fused to each other, otherwise free; petals of inner whorl 2 or 3, (2-)2.5-3.5 X (0.5-)0.75-1.2 cm, slightly concave, slightly asymmetric, narrowly elliptic to almost oblong, basally attached to stamens for 2-2.5(—3) mm; sepals lacking; perules undifferentiated, often 6 to 10 in 2 uneven whorls, often unevenly triangular, dark brown, finely hairy, 1-3(—4) X 1-3.5(—5) mm, deciduous, not present on mature flowers and fruit; stamens (25 to)35 to 45, glabrous, light yellow, later yellowish brown, in a circular to asymmetrically elliptic formation 1.3-2(—3) cm diam.; filaments white-yellow to yellowish green, (0.8-)1-2 cm X 1-2 mm, glabrous, laterally compressed, straplike, slight­ly curved, basally fused to each other and to petals of the inner whorl for 2-2.5(—3.5) mm, thus forming a shallow ring; anthers 2-lobed (locules distinct), 1-1.2 X 1 mm or less, light yellow, later brownish yellow, basifixed or nearly so; style single, columnar, sinuous, proximally shortly and densely hairy, less so distally, 2-2.5(—3.2) X 1-1.5 mm proximally; stigma light brown to brown, divided into 3 indistinct lobes that are <1 mm diam.; ovary superior, rounded, almost conical, 3(4)-carpellate, finely and densely tomentose, yellowish green, 2.5-3(—4) X 3-3.5(—3.7) mm. Mature fruit unevenly globose elliptical, always longer than wider, mid- to dark brown, densely hairy, with hairs short and whitish, 3-valved, 2-3 X 2-2.5 cm, not always containing 3 seeds; mature seed light brown, not shiny, laterally compressed, unevenly and finely hairy, 1-1.5 cm diam.

Camellia ligustrina Orel, Curry & Luu.

A. Adult leaf, primary and secondary venation, adaxial view. —B. Adult leaf, primary and secondary venation, shape variation, adaxial view. —C. Adult leaf, primary and secondary venation, abaxial view. —D. Terminal leaf bud. —E. Undifferentiated perules, distal whorl. —F, G. Undifferentiated perules, proximal whorl. —H—J. Petals, outer whorl. —K—M. Petals, inner whorl. —N. Developing flower bud. —O. Anthers. —P. The apex of the style. —R. Lateral view of mature flower, schematic diagram. —S. Adult fruit capsule. —T. Branch with flowers and leaves. Drawn from the holotype G. Orel & A. Curry 0734 (NSW, SGN).

Distribution and ecology

Camellia ligustrina is known only from the type location in Lam Dong Province in Vietnam. The type specimen was found at 1850 m, near the summit of Mt. Lang Biang, which reaches 2163 m. The area of the type location is covered by dense, ever-wet rainforest, and C. ligustrina seems to thrive in poor, wet, but well- drained soils, under low-light conditions.

IUCN Red List category

The AOO for this new species is estimated to be less than 1 km2. Despite a further search of the area around the type locality, only seven additional mature plants were located, and a smaller number of immature plants were also found. The total known population of the species is fewer than 50, and it would qualify for assessment as Critically Endangered (CR) under criterion D (IUCN, 2011). However, the area is adequately protected by inclusion in the Bidoup-Nui Ba National Park, and this suggests that the IUCN category of Endangered (EN) would be more appropriate (IUCN, 2011).

Phenology

Camellia ligustrina was collected in flower in mid-December. The relatively small number of mature flowers and immature flower buds observed for the new species may indicate that October through November is the main flowering period. The presence of a small number of mature fruits was also noted at the mid-December collection.

Etymology

The specific epithet refers to the striking, but superficial, resemblance of the foliage to Ligustrum lucidum W. T. Aiton (Oleaceae).

Discussion

The new species Camellia ligustrina was found within a geographical area that contains mostly tropical, large-leaved, rainforest Camellia species (Sealy, 1958; Gao et al., 2005; Orel, 2006; Orel & Wilson, 2010b, 2012). Thus its distribution may be judged as somewhat atypical since it is morphologically closer to cool temperate or margin­ally subtropical Camellia species. The striking morphology of C. ligustrina—that is, the relatively small size of its foliage and the white color and small size of its flowers—may be due to the elevation where the type specimen was found, ca. 1850 m.

Camellia ligustrina possesses narrowly elliptic to elliptic leaves; sessile to almost sessile, perulate flowers; straplike outer stamens that are basally fused for 2-3 mm; a hairy and almost conical ovary with a single, sinuous, and columnar style up to 3 cm long. Moreover, these characters, combined with the unevenly globose to elliptical, densely hairy, 3-valved fruit and, the light brown, unevenly and finely hairy seeds, are firm indications that C. ligustrina is only superficially similar to any of the Camellia species described and contained in the 12 published sections recognized by Sealy (1958). Owing to the combina­tion of its unique morphological characteristics, C. ligustrina merits placement in its own section, Camellia sect. Pierrea