Pogostemon hainanensis L.X. Yuan & Gang Yao, 2022

Yuan, Langxing, Tan, Gan, Zhang, Wenhua, Xue, Bine, Deng, Jiwen, Liu, Lei & Yao, Gang, 2022, Molecular and morphological evidence for a new species of Pogostemon (Lamiaceae) from Hainan Island, China, PhytoKeys 188, pp. 177-191 : 177

Pogostemon hainanensis L.X. Yuan & Gang Yao sp. nov.

Figures 2 , 3

Diagnosis.

The species is similar to Pogostemon parviflorus Benth. in general morphology, but differs from the latter by its leaves margin obviously double serrate, petioles usually 4.5-11.5 cm long, spikes of inflorescence up to 8 cm long, calyx 4-5 mm long, corolla 6-7 mm long, and the calyx teeth is 2/3 to subequal as long as the calyx tube.

Type.

China. Hainan province, Yinggeling Nature Reserve, Nanleshan, Fanyang , Wuzhishan , 18°54'38.25"N, 109°22'26.58"E, at an elevation of about 570 m, 6 February 2021, L.X. Yuan 20210206001 (holotype, IBSC; isotypes: IBSC, KUN) .

Description.

Perennial herbs or shrubs, 0.8-2 m tall. Stem erect, 6-8 mm in diameter, 4-angular, slightly dilated at nodes, a few branched, strigose, or villous at the upper part. Leaves opposite; blade ovate, rarely ovate-lanceolate, (5.5-) 9-13.5 × (2.5) 6.5-10.5 cm, papery or membranous, strigose on both surfaces, base broadly cuneate, margin obviously double serrate, entire at base, apex acuminate; midvein elevated abaxially, lateral vein 3-4 (rarely 5) pairs on each side of the midvein, slightly elevated abaxially; petioles (1.5-) 4-11.5 cm long, ca. 1 mm in diameter, strigose. Spikes of inflorescence (1.0-) 2.5-8.0(-10.5) cm long, 9-12 mm in diameter, terminal and axillary, interrupted basally in long spikes, usually with more than two lateral branches; peduncle (1-) 2-4 cm long, densely villous; verticillasters many-flowered, flowers sessile. Bracts oblong, 5-13 × 2.5-5 mm, strigose, midvein elevated abaxially, lateral vein 1-2 pairs on each side of the midvein or sometimes obscure; bracteoles ovate-lanceolate to narrowly lanceolate, 2.5-5 × 0.7-1.8 mm, strigose. Calyx tubular-inflated, 4-5 mm long, 5-veined, strigose and sparsely golden glandular outside, sometimes sparsely strigillose inside at the upper part of tube; teeth 5, narrowly triangular, equal, 1.8-2 mm long, 0.6-0.8 mm wide at base, 2/3 to subequal as long as the calyx tube, subglabours or strigillose inside. Corolla white, 6-7 mm long, exserted evidently from calyx, 2-lipped, upper lip 3-lobed, lower lip entire. Stamens 4, erect, much exserted from corolla; filaments 7-7.5 mm long, all inserted at a height of ca. 2 mm in the tube, bearded at middle, bearded portion exserted; anther 1-locular, cell apex dehiscent. Style 7-7.5 mm long; stigma bifid, lobes subequal, 1.2-1.7 mm long. Disc ca. 0.6 mm long. Nutlets 4, ca. 0.7 × ca. 0.6 mm long, ellipsoid or slightly depressed globose, abaxially slightly flat, adaxially ribbed, black or dark brown.

Etymology.

Pogostemon hainanensis is named after its type locality, Hainan province, China.

Phenology.

Flowering from December to the next February and fruiting from January to April.

Paratype.

China. Hainan Province, Lingshui Hsien, 12 January 1934, near river, Z. Huang 36483 (IBSC-0585902!); Ledong Hsien, Jiaxi Nature Reserve, 18°52'35.85"N, 109°10'36.99"E, at an elevation of about 800 m, 7 February 2021, L.X. Yuan 20210207001 (IBSC); Baoting Hsien, near the Tiantan waterfall, 18°42'16.17"N, 109°41'50.55"E, at an elevation of about 560 m, 25 April 2021, L.X. Yuan 20210425001 (IBSC).

Distribution and habit.

The new species is endemic to Hainan Province, China (Figure 4 ). It grows under forests, usually near ravines, at an elevation of 550-800 m.

Chinese name.

Hai Nan Ci Rui Cao (海南刺蕊草).

Figures

Figure 2. Habit of Pogostemon hainanensis.

Figure 3. Pogostemon hainanensis A branch B leaf C, D leaf E spike of inflorescence F stem G cross section of stem H bract (the left one) and bracteoles (the right two) I, J flower K calyx L nutlets.

Figure 4. Distribution of Pogostemon hainanense (red circular).