Pogostemon dielsianus Dunn (1913: 159)

YAO, GANG, DENG, YUN-FEI & GE, XUE-JUN, 2015, A Taxonomic Revision Of Pogostemon (Lamiaceae) From China, Phytotaxa 200 (1), pp. 448-450 : 448-450

4. Pogostemon dielsianus Dunn (1913: 159) . Type: — CHINA. Yunnan: Fugong, Salween-Irrawaddy divide and valley of the Salween , 26°20' N, 1500–1800 m, November 1905, G. Forrest 875 (holotype E!, isotype K!).

Perennial shrubs, to 3 m tall, branched. Stems solid, terete or angular, glabrous. Leaves opposite; petiole 0.5–1 cm long; blade linear-lanceolate to lanceolate, 9–14 × 2–3.5 cm, papery, base cuneate-attenuate, margin serrate, apex acminate, adaxially subglabrous, abaxially sparsely strigose-puberulent, lateral veins 5–7 pairs on each side of midvein. Spikes 3.5–7 cm long, 8–12 mm wide, terminal and axillary, subcontinuous, basally somewhat lax, with more than two lateral branched, densely appressed pubescent except for corolla, pedunculate, 0.5–2 cm long; verticillasters sessile, 10–14-flowered, flowers sessile. Bracts lanceolate, subequal to or shorter than the calyx. Calyx tubular, 3.5–4.5 mm long, 5-veined; teeth 5, triangular, 1/5–1/4 as long as the calyx tube. Corolla rose, 7–8 mm long, much exserted, tube cylindric, dilated at throat. Stamens 4, exserted from corolla; filaments 6.2–7 mm long, exserted portion 3.5 mm. Style ca. 6.4 mm long; stigma bifid, lobes ca. 1.2 mm. Disc ca. 0.7 mm long. Nutlets 4, ca. 1.5 × 0.8 mm, lanceolate.

Distribution and habitat:— The species is only known from its type locality, western Yunnan of China ( Figure 2 ). It grows amongst rocky scrub on dry rocky hillsides, at the elevation of 1700–1800 m.

Phenology:— Flowering in November.

Taxonomic notes:— Only the type of Pogostemon dielsianus was examined. This species is similar to P. elsholtzioides and P. griffithii Prain (1908: 181) in having lanceolate leaves. Pogostemon dielsianus differs from P. elsholtzioides in having larger flowers, the corolla being 7–8 mm long (not ca. 4.5 mm long) and a tubular (not campanulate) calyx, and differs also from P. griffithii in larger flowers with the corolla 7–8 mm long (not ca. 5 mm long) and a tubular (not campanulate) calyx. Pogostemon dielsianus and P. elsholtzioides have narrowly ovoid nutlets, whereas P. griffithii has cylindrical nutlets. In addition, the ratio of the length of calyx teeth and calyx tube in P. dielsianus , P. elsholtzioides , and P. griffithii is 1/5–1/4, 1/3–1/2 and 1/2–1 respectively.

POGOSTEMON ( LAMIACEAE )

Phytotaxa 200 (1) © 2015 Magnolia Press • 11

Figures

FIGURE 2. Distribution maps of Pogostemon amaranthoides, P. chinensis, P. dielsianus and P. elsholtzioides.