Isodon delavayi C.L. Xiang & Y.P. Chen, 2014

Chen, Ya-Ping, Hu, Guo-Xiong & Xiang, Chun-Lei, 2014, Isodon delavayi (Ocimeae, Nepetoideae, Lamiaceae): a new species from Yunnan Province, Southwest China, Phytotaxa 156 (5), pp. 291-297 : 292-295

Isodon delavayi C.L. Xiang & Y.P. Chen , sp. nov. ( Figure 1 & Figure 2 )

Isodon delavayi is similar to I. scoparius (C.Y. Wu & H.W. Li 1977: 777) H. Hara (1985: 236) and I. pharicus ( Prain 1891: 297) Murata (1955: 15) , but differs from the former in stems much branched and 15–40 cm long (vs. 40–100 cm in I. scoparius ), leaves entire (vs. serrate in I. scoparius ), cymes 1–3-flowered (vs. 3–5-flowered in I. scoparius ), as well as calyx lobes ovate-triangular (vs. linear-lanceolate in I. scoparius ) and 1.2 mm long (vs. 2.5–3 mm in I. scoparius ), from the latter in leaves entire and glabrous (vs. crenate, glandular puberulent, and puberulent in I. pharicus ), petiole obsolete (vs. 1–4 mm long in I. pharicus ), and cymes 1–3-flowered (vs. 3–7-flowered in I. pharicus ).

TYPE: — CHINA. Yunnan: Eryuan County, Menghuoying Village, Mt. Yangyu , elev. 2500 m, 26°11′08.7″N, 100°01′30.2″E, on the open and rocky slope, 21 October 2012, C.L. Xiang, G.X. Hu & Y.P. Chen. 541 (holotype KUN! , isotypes K! , KUN! , PE! ).

Shrubs 15–40 cm. Rhizomes woody, 3–7 mm diam., twisted. Stems erect, numerous and much branched, 1–4 mm diam., obtusely 4-angled or subterete; branches gray, glabrescent; branchlets brown to purplish, densely puberulent. Leaves decussate, rarely in whorls of 3; internode (0.3–) 0.5–1 (–2) cm long; lamina ovate-elliptic, narrowly elliptic or lanceolate, 0.5–2 × 0.2–0.6 cm, thick papery, base cuneate to subrounded, margin entire, apex acute, adaxially olive green, abaxially green, both surfaces glabrous and sparsely yellowish glandular, lateral veins 3- or 4- paired; petiole obsolete to ca. 1 mm long. Cymes axillary, 1–3-flowered, densely glandular puberulent and puberulent; peduncle 0.5–1 cm long; floral leaves gradually reduced toward apex, usually shorter than cymes; bracteoles linear, ca. 1 mm long; pedicel 2–3 mm long. Calyx campanulate, ca. 2.5 mm long, purplish, densely glandular puberulent and glandular, yellowish glandular, slightly 2-lipped; lobes subequal, ca. 1/2 as long as calyx, ovate-triangular, lower 2 slightly longer, apex acute; fruiting calyx dilated to ca. 5 mm long, slightly curved. Corolla bluish purple, ca. 7 mm long, puberulent and glandular outside; tube ca. 4 × 2 mm, saccate abaxially near base; 2-lipped, posterior lip 4-cleft, erect, ca. 2.5 mm long, anterior lip entire, concave, navicular, ca. 3 mm long. Stamens 4, base puberulent, included within corolla. Style included, apex 2-cleft. Mericarps brownish, elliptic, ca. 1.5 × 1 mm, glabrous. Fl. Sep–Oct, fr. Oct–Nov.

Leaf epidermis morphology:— Figure 3 demonstrates adaxial ( Figure 3A ) and abaxial surfaces ( Figure 3B ) of leaf of I. delavayi . Both sides are glabrous and sparsely covered with glands. Stomatal apparatuses can only be found in abaxial epidermis and are irregular.

Pollen morphology:— Pollen morphology of the new species is shown in Figures 3C–E . As we can see that pollen grains of I. delavayi are hexacolpate, which is one of the shared characters of subfamily Nepetoideae ( Erdtman 1945, Cantino & Sanders 1986). The ornamentation of exine is bireticulate. Polar axis (P) = 41.9 ± 2.49 µm, equatorial axis (E) = 37.1 ± 2.97 µm. Pollen shape is prolate (P/E = 1.136 ± 0.085).

Mericarp morphology:— Figure 3F shows the shape and size of mericarp of I. delavayi . Length (L) = 1.52 ± 0.087 mm, width (W) = 1.10 ± 0.033 mm. Shape of the mericarp is elliptic. The surface sculpturing is papillate.

Distribution, habitat, and phenology:— According to present collections, I. delavayi is only known from Mt. Yangyu, Eryuan County, Yunnan Province. This rare species grows on open and rocky slopes between 2400 m and 2600 m at elevation. The vegetation in this place is mainly formed by herbaceous and shrubby plants such as Ajania sp. , Cotoneaster sp. , Dracocephalum forrestii W.W. Sm. , Eulalia . sp., Isodon calcicolus (Hand.-Mazz.) H. Hara, Leontopodium sp. , Onosma sp. , and Premna sp. Future fieldwork may expand its distribution area and habitat. Flowering time of I. delavayi is between September and October, and fruiting time from October to November.

Etymology:— The new species is named after its former collector M. I'Abbé Delavay, who was a very famous French missionary and plant collector of the 19th century.

Additional specimens examined (paratypes): — CHINA. Yunnan: Eryuan County, Menghuoying Village, Mt. Yangyu , elev. 2500 m, 26°11′08.7″N, 100°01′30.2″E, on the open and rocky slope, 21 October 2012, C.L. Xiang, G.X. Hu & Y.P. Chen. 540, 542 ( KUN!) ; at the same place, 19 October 1887, M. I'Abbé Delavay 2707 ( KUN!) ; Yunnan: M. I'Abbé Delavay 2922 ( KUN!) .

Figures

FIGURE 1. Isodon delavayi. A) habit; B) leaf; C) calyx; D) flower in lateral view; E) opened flower; F) pistil; G) mericarp.

FIGURE 2. Isodon delavayi. A) habitat; B) habit; C) much branched plant; D) whorled leaves; E) leaf; F) inflorescence; G) flower in lateral view; H) infructescence.

FIGURE 3. Scanning electron micrographs of leaf epidermis, pollen grain, and mericarp of Isodon delavayi. A) adaxial surface of leaf, showing the glands; B) abaxial surface of leaf, showing the glands and stomata; C) whole pollen, polar view; D) whole pollen, equatorial view; E) exine surface of pollen; F) mericarp.