Lanonia hexasepala (Gagnepain) Henderson & Bacon (2011: 893)

Henderson, Andrew & D ựng, Nguy ễn Qu ốc, 2022, A revision of Lanonia (Arecaceae, Coryphoideae, Livistoninae), Phytotaxa 532 (3), pp. 209-245 : 227-229

9. Lanonia hexasepala (Gagnepain) Henderson & Bacon (2011: 893) .

Licuala hexasepala Gagnepain (1937: 155) . Lectotype (designated by Henderson & Bacon 2011):— VIETNAM. Annam, Mère et l’Enfant près de Nhatrang, 1,200 m, 4 November 1929, E. Poilane 5059 (lectotype P! isolectotype F!).

Stems 1.4(1.0–2.0) m long, 1.6(0.6–2.0) cm diameter, clustered or solitary. Leaves number not recorded; ligules 10.4(8.0–13.0) cm long, papery, not disintegrating into fibers; sheaths and proximalmost part of petioles with dense, flat, black scales; petioles 32.0(16.0–46.5) cm long, 0.3(0.2–0.4) cm wide at the apex; petiole thorns usually stout, reddish-brown or dark brown, some bifid or often some in pairs, on proximalmost part of petiole; hastulas flat, rounded, not infolded; leaf blades 25.7(20.0–30.0) cm wide; costas 1.1(0.4–2.0) cm long, triangular, with a pulvinus at the apex abaxially, with the numerous segments free almost to the base; segments 11(6–13) per leaf, not mottled, with minute, reddish-brown scales abaxially, with (on dried specimens) straight or rarely ruffled margins; middle segments 20.0(16.2–24.0) cm long, 2.3(1.6–3.4) cm wide at the apex; apices of middle segments with adaxial splits much deeper than abaxial ones. Inflorescences 60.0 cm long; prophylls 16.5 cm long; peduncles 37.0 cm long; rachis bracts narrowly tubular, splitting apically, not or sparsely tomentose; rachillae filiform, sparsely to moderately covered with short, mostly simple, brownish hairs; staminate rachises absent; staminate partial inflorescences 1, branched to 2–4 orders; staminate rachillae 22(21–23), 12.3(6.5–18.0) cm long, 0.6(0.5–0.6) mm diameter; staminate flowers 1.5 mm long; sepals not pedicellate at the base, not densely hairy; petals rounded at the apex; stamens with alternately long and short filaments and small, almost square anthers; filaments not elongate; pistillodes undivided; pistillate rachises absent; pistillate partial inflorescences 1, branched to 2–3 orders; pistillate rachillae on proximalmost partial inflorescence 8(7–9), 9.4(6.0–11.5) cm long, 0.6(0.4–0.7) mm diameter; pistillate flowers 2.1(2.0–2.2) mm long, with short styles; fruits 7.0 mm long, 7.1(6.9–7.2) mm diameter, globose, color not recorded, with rough, pebbled surfaces; seeds with a straight basal intrusion.

Distribution and habitat:— Southern Vietnam in Dak Lac, Khanh Hoa, and Ninh Thuan provinces in montane rainforest at 1,479(900–1,800) m elevation ( Fig. 10 ).

Taxonomic notes:— Specimens determined as preliminary species Lanonia hexasepala were polymorphic for stem branching, hastula shape, leaf mottling, segment margins, rachis bracts, and rachillae thickness. Therefore the preliminary species was split into several species such that variables were consistent within each one (except that stem branching and leaf mottling were treated as traits; mottling is known for only a few specimens). However, one of these species could not be justified morphologically or geographically, and so segment margins were polymorphic in one phylogenetic species. Four different phylogenetic species were recognized, L. hexasepala , L. honbaensis , L. montana , and L. tenuisecta .

Lanonia hexasepala is notable for its elongate, papery ligules, sheaths and petioles with dense, flat, black scales, and stout, reddish-brown or dark brown, sometimes bifid, petiole thorns. It shares these character states with L. honbaensis , L. manglaensis , L. montana , and L. tenuisecta and the five appear closely related.

Subspecific variation:— Lanonia hexasepala is known from four separate, montane areas—Chu Mu (formerly known as La Mère et l’Enfant); Chu Yang Sinh; Hon Giao; and Phuoc Binh). Of the two specimens known from Chu Yang Sinh, one (Averyanov 6180) has segments with ruffled margins.

Henderson & Nguyễn Qu ốc Dựng (2019) discussed variation in Lanonia hexasepala and noted one population from further south than the others, in Lam Dong province. This was based on three specimens (Henderson 4158, 4161, 4162; a fourth specimen, Schmid s.n., may also belong here). These specimens have the elaborate flower bracteoles found in L. hexasepala , and appear related to that species. However, they are confusingly variable. One (Henderson 4162) has the middle segment split or not split and a staminate and pistillate inflorescence on the same plant. Another (Henderson 4161) has the apices of middle segments with adaxial splits much deeper than abaxial ones, but in the other two specimens the middle segment splits are not much deeper. Because of this variation, these specimens remain unidentified. More specimens from this area are needed to understand this population.

Figures

FIGURE 10. Distribution maps of L. hainanensis, L. hexasepala, L. honbaensis, and L. honheoensis.