Henckelia inaequalifolia Li H. Yang & X.Z. Shi, 2021

Shi, Xi-Zuo, Wang, Jia-Cai & Yang, Li-Hua, 2021, Henckelia inaequalifolia (Gesneriaceae), a new species from Sichuan, China, Phytotaxa 518 (1), pp. 54-60 : 54-58

Henckelia inaequalifolia Li H. Yang & X.Z. Shi , sp. nov. (Figs. 1, 2 and 3A–E)

Diagnosis: —The new species mainly differs from Henckelia bifolia (D. Don) A. Dietr. (1831: 574) by its stem [often 2 (rarely 1 or 3) internodes; the lower most internode is obvious and the internode above the large pair of leaves is gradually weak vs. 1 obvious internode], petiolate leaf (vs. sessile), and solitary axillary flowers without bracts [vs. 1–2 (rarely 3)-flowered cymes with 2 bracts]. The new species also resembles H. amplexifolia Sirim. in Sirimongkol et al. (2019: 45), but differs from the latter by its asexual reproduction habit (with resting shoots at the base of stem vs. with bulbils on the stolon), petiolate leaf (vs. sessile), solitary axillary flowers without bracts (vs. 3–9-flowered cymes with 2 bracts), and infundibuliform and 4.5–5 cm long corolla tube (vs. campanulate, ca. 0.5 cm long).

Type: — CHINA. Sichuan Province: Hongya County, Yupingshan , alt. 1128 m, 29°46′21.46″N, 103°11′26.53″E, 19 April 2021, Li-Hua Yang & Xi-Zuo Shi YLH1184 (holotype: IBSC-0865764!; isotypes: IBSC-0865765!, IBSC-0865766!) .

FIGTURE 1. Henckelia inaequalifolia Li H. Yang & X.Z. Shi. ( A) habit, ( B) habit from below, ( C) opened corolla showing stamens and staminodes, (D) calyx, ( E) pedicel of the solitary flower, ( F) flower in oblique front view, ( G) pistil, ( H) flower in side view. Red arrows show the small leaves. All photos were taken from the type locality by Li-Hua Yang.

FIGTURE 2. Holotype (IBSC-0865764) of Henckelia inaequalifolia Li H. Yang & X.Z. Shi.

FIGTURE 3. Henckelia inaequalifolia Li H. Yang & X.Z. Shi. ( A – E) and three other species ( F – H) with a small lanceolate leave at the opposite position of a large one. ( A) habitat, ( B) flowering plants in nature, ( C) flower in front view, (D) flower in side view, ( E) fruiting plant, ( F) H. fruticola (H.W. Li) D.J. Middleton & Mich. Möller , ( G) H. speciosa (Kurz) D.J. Middleton & Mich. Möller , ( H) H. grandifolia A. Dietr .. Red arrows show the small leaves. Photos of H. inaequalifolia were taken from its type locality, and photos of H. fruticola , H. speciosa , and H. grandifolia were taken from greenhouse of SCBG. All photos were taken by Li-Hua Yang.

Perennial herbs, caulescent, with resting shoots at the base of stem in winter; stem erect, cylindrical, often 2 (rarely 1 or 3) internodes; the lowermost internode 2–4 cm long; the internode above the large pair of leaves is gradually weak. Leaves opposite, 1–3 pairs; the bottom pair of leaves have the largest leaf and are extremely unequal in size; small leaf blade 1–1.5 × 1–1.2 cm, or sometimes absent; the larger leaf blade oval, 12–14 × 8–10 cm, adaxially pubescent, abaxially pubescent along veins, lateral veins 6–8 on each side of midrib, margin serrate, base cordate to orbicular; petioles pubescent, 2–2.5 cm long. Cymes reduce to solitary axillary flowers; pedicels pubescent, 1.5–2 cm long, ca. 0.2 cm in diameter. Calyx 5-lobed, fused into a tube for half of length; lobe narrowly triangle to broadly lanceolate, 1.3–1.6 × 0.3–0.5 cm, apex acuminate, margin entire, outside pubescent, inside glabrous. Corolla 6–7.5 cm long; corolla tube white, with a larger yellow spot and a network of reddish stripes at throat, infundibuliform, 4.5–5 cm long, 1.2–1.5 cm in diameter at throat, outside pubescent, inside glabrous; limb blue-purple, distinctly 2-lipped; adaxial lip 2-lobed, lobes semicircular, 1.2–1.5 × 1–1.2 cm, apex rounded, abaxial lip 3-lobed, lobes broadly oblong, 1.5–1.8 × 1.2–1.5 cm, apex rounded. Stamens 2; filaments adnate to ca. 2.5 cm above corolla tube base, strongly geniculate just under middle, swollen at bend, twisted in lower half, sparely pubescent near the top; anthers coherent face to face, ca. 4 × 3 mm, sparely glandular pubescent. Staminodes 3, glabrous; lateral staminodes 2, ca. 4 mm long, and central staminode ca. 1 mm long. Pistil 4.5–5 cm long; stigma chiritoid, deeply 2-lobed, ca. 6 mm long; style ca. 12 mm long, pubescent; ovary 2.5–3 cm long, densely pubescent; disc annular, ca. 1 mm in height. Capsule linear, 11–15 cm long, pubescent.

Phenology: —Flowering April to May, and fruiting from June to August.

Etymology: —The specific epithet is based on the extremely unequal-sized leaves in a pair of this new species.

Vernacular name: —The Chinese mandarin “Bu Deng Ye Han Ke Ju Tai” (不Ỵ叶汉克ffḋ).

FIGTURE 4. Geographic distribution of Henckelia inaequalifolia Li H. Yang & X.Z. Shi (triangle), H. amplexifolia Sirim. (square) and H. bifolia (D. Don) A. Dietr. (dots).

Distribution and habitat: —At present, this new species is only known from the type locality (Fig. 4), and ca. 200 mature individuals were found here. The plants were found growing under evergreen broad-leaved forests along a brook on moist rocks.

Discussion: — Henckelia inaequalifolia is similar to H. bifolia and H. amplexifolia in its habit and unequal size of leaves; however, these three species can be distinguished from each other by a combination of characters summarized in table 1 . Additionally, the character, solitary axillary flower, of this new species is the first report in the genus Henckelia . Actually, the reduction of the cymes to solitary flowers is also uncommon in the whole family Gesneriaceae and only occurred in few New World genera ( Weber 2013), such as Gloxinia L’ Hér., Gloxiniopsis Roalson & Boggan , Smithiantha Kuntze and Diastema Benth.

Interestingly, the unequal size of the leaves also appears in some other species of Henckelia , such as H. speciosa (Kurz) D.J. Middleton & Mich. Möllerin Weber et al. (2011: 777) , H. fruticola (H.W. Li) D.J. Middleton & Mich. Möller. in Weber et al. (2011: 775) and H. grandifolia A. Dietr. (1831: 576) . However, the gross morphology of the new species shows obvious differences to the latter three species. For these three species, H. speciosa , H. fruticola and H. grandifolia , previous morphological observations based on dry specimens revealed an alternate phyllotaxis ( Wood 1974, Wang et al. 1998). Nevertheless, our study using living materials shows that all these three species actually possesses opposite phyllotaxis, with a small lanceolate leave at the opposite position of a large one (Fig. 3F–H). Our study also offers a caution to the alternate phyllotaxis described in some other species, such as H. lachenensis (C.B. Clarke) D.J. Middleton & Mich. Möller in Weber et al. (2011: 776) and H. repens (Bedd.) A. Weber & B.L. Burtt (1998: 354) . Further detailed morphological observations are needed to address this question. Our study highlights the necessity of field investigation and morphological observation based on living materials for the good taxonomy in Gesneriaceae ( Chen et al. 2020, Shi & Yang 2021).

Additional specimen examined (paratypes): — CHINA. Sichuan Province: Hongya County, the same locality as types, 13 August 2020, Li-Hua Yang et al. YLH1112 (IBSC-0865088!, IBSC-0865089!, IBSC-0865087!) .