Calamus clivorum Henderson & Nguyen Quoc Dung 2018, sp. nov.
Creators: name: Henderson, Andrew
name: Dung, Nguyen Quoc
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Arecales
Arecaceae
Calamus
Calamus clivorum

description: Calamus clivorum Henderson & Nguyen Quoc Dung sp. nov.   
 Type:— VIETNAM. Tourane and vicinity, May–July 1927, J. & M. Clemens 4485 (holotype P!). Fig. 2.   
 It differs from similar species (C. compsostachys, C. spiralis) in its pinnae without brown scales abaxially and pistillate inflorescences branched to 1 order.   
 Stems branching not recorded, climbing, length not recorded, 0.6 cm diameter. Leaf sheaths tubular, closed opposite the petiole, with a knee below the petiole; leaf sheath spines short, needle-like, swollen-based, in small groups of 1 main spine and smaller lateral spines, especially near sheath apex; ocreas short, membranous, spinulose, with external and internal abscission zone, splitting and falling early; flagella vestigial; petioles 1.0 cm long; rachises 2.2 cm long, the apices extended into a cirrus narrower than the rachis and not continuous with it adaxially, without vestigial pinnae, with scattered, solitary spines, terminating in a slender axis; pinnae 2 per side of rachis, irregularly arranged, elliptic, without spinules on veins, the lateral veins diverging then converging, both terminating apically or slightly subapically; proximalmost pinnae swept back across the sheath; middle pinnae 9.0 cm long, 1.4 cm wide. Inflorescences diverging from sheath near sheath apex, with two diverging ridges distal to point of divergence; inflorescences erect, slender, short, without recurved spines on rachis and rachis bracts abaxially, without a flagellum-like apex; partial inflorescences not stalked, with a pulvinus in axil of rachis and partial inflorescence; rachis bracts tubular, narrow, persistent, closely sheathing the rachis, not swollen at the apex; rachillae sessile; staminate inflorescences not recorded; pistillate inflorescences branched to 1 order, 6.0 cm long; pistillate rachillae 1.0 cm long, with dyads of 1 pistillate and 1 neuter flower; fruits globose, 15.2 mm long, 10.6 mm diameter, color not recorded; fruiting perianths not recorded; fruit scales channeled vertically; seeds 1 per fruit, basally attached, small, globose, with a ventral depression, reniform in longitudinal section, the dorsal surfaces grooved, covered with a tanniniferous, non-fibrous sarcotesta; raphe branches not bifurcating from the attachment of the seed; endosperm homogeneous; embryos at or near base of seed.   
 Distribution and habitat:—Central Vietnam in lowland areas.   
 Taxonomic notes:— Calamus clivorum is known from a single specimen collected in 1927 at “Tourane and vicinity” (Tourane is the colonial name for Da Nang). It has not been recollected, and not found on recent searches of the area. The label states: “small, base of stony hill. Fd. in thicket of Melastoma, Grewia, Glochidium, Rub. ” Because there is only one specimen, and this is rather poor, the relationships of this unusual species are not clear. The leaf sheath spines are similar to those of C. spiralis. The cirrus is interpreted as being the same as that of C. compsostachys and C. spiralis, with the cirrus narrower than the rachis and not continuous with it adaxially. This condition is found only in these three species of Calamus.   
  Calamus gracilis Roxburgh (1832: 781).  Palmijuncus gracilis (Roxburgh) Kuntze (1891: 733). Lectotype (designated here):— BANGLADESH. India Orientalis, no date, W. Roxburgh s.n. (lectotype BM!, isolectotype BR!).   
 Stems clustered or rarely solitary, climbing, 11.7(2.0–26.0) m long, 1.1(0.4–1.9) cm diameter. Leaf sheaths tubular, closed opposite the petiole, with a knee below the petiole, mottled with irregular bands of tomentum; leaf sheath spines short, scattered, sometimes upward-pointing, with a distinct swelling at the base adaxially; ocreas short, membranous, non-spiny, forming an irregular ring but usually open or reduced above the petiole, splitting early; flagella well-developed; petioles 4.9(0.1–20.0) cm long; rachises 37.5(22.7–60.0) cm long, the apices filiform or sometimes just a short stub between the distal pair of pinnae; pinnae 17(10–29) per side of rachis, arranged in remote clusters, the pinnae of a cluster spreading in different planes, lanceolate, with spinules on veins adaxially, the lateral veins approximately parallel, one terminating subapically, leaving a distinct or obscure, adaxial ‘broken’ vein; proximalmost pinnae swept back across the sheath (on adult plants only); middle pinnae 19.3(13.0–25.5) cm long, 1.6(0.7–3.0) cm wide; distal pair of pinnae joined at their bases for 1.3(0.1–3.5) cm. Inflorescences diverging from sheath near sheath apex, with two diverging ridges distal to point of divergence; inflorescences arching, slender, elongate, with solitary or grouped, recurved spines on rachis and rachis bracts abaxially, usually terminating in a flagellum-like apex; partial inflorescences not stalked, with a pulvinus in axil of rachis and partial inflorescence; rachis bracts tubular, narrow, persistent, closely sheathing the rachis, not swollen at the apex, sometimes partially splitting if the partial inflorescence inserted below the bract apex; rachillae sessile; staminate inflorescences branched to 3 orders, length not recorded; staminate rachillae 2.2(2.0–2.3) cm long; staminate flowers arranged in alternate, opposite rows; staminate sepals shorter than the petals, cupular, 3-lobed at the apex; stamens 6; filaments uniseriate, inflexed at the apex; pistillate inflorescences branched to 2 orders, 90.0 cm long; pistillate rachillae 4.2(3.0–5.5) cm long, with dyads of 1 pistillate and 1 neuter flower; fruits ellipsoid, 23.1(19.3-28.8) mm long, 14.7(11.9–17.5) mm diameter, orange or red-brown; fruiting perianths tubular; fruit scales channeled vertically; seeds 1 per fruit, basally attached, large, ellipsoid, not reniform in longitudinal section, the dorsal surfaces pitted, covered with a tanniniferous, non-fibrous sarcotesta; raphe branches 2, bifurcating from the attachment of seed and running along ventral side; endosperm with numerous, deep, pit-like ruminations; embryos lateral in seed.   
 Taxonomic notes:— There is geographic disjunction in the distribution of Calamus gracilis, and two subgroups of specimens can be recognized—from central and southern Vietnam, and from Bangladesh, northeastern India, northern Myanmar, China (Hainan, Yunnan), and Laos. Specimens from central and southern Vietnam differ significantly from the others in three variables (rachis length, number of divisions, pinnae width)(t -test, P <0.05), with specimens from Vietnam having longer rachises and more, narrower pinnae. Based on these results, specimens from the two regions are recognized as subspecies (subspp. gracilis, vietnamensis).
description: Published as part of Henderson, Andrew & Dung, Nguyen Quoc, 2018, New species and subspecies of Calamus (Arecaceae) from Vietnam, pp. 251-262 in Phytotaxa 347 (4) on pages 252-255, DOI: 10.11646/phytotaxa.347.4.1, http://zenodo.org/record/13707821