Didymocarpus heucherifolius var. gamosepalus can be distinguished from D. heucherifolius var. heucherifolius by its calyx base connate, 5-lobed from middle to above middle, glabrous corolla ca. 5 cm long, stamens 2.3 cm from the base, staminodes 1.4–1.8 cm from the base and 3.6–4.3 cm pistil. It also can be distinguished from D. heucherifolius var. yinzhengii by its calyx base connate, 5-lobed from middle to above middle, stamens 2.3 cm from the base, staminodes 1, pistil 3.6–4.3 cm.

CHINA. Guangxi Province, cultivated in the nursery of Gesneriad Conservation Center of China (GCCC), introduced from north of Guangdong Province: Pingyuan County, Meizhou City, growing in rocky crevices at the foot of a calcareous sedimentary rocky hill. 22 February 2019, flowering, WF20190222-05 (holotype: IBK; isotype: AHU)

Acaulescent perennial herb. Rhizome horizontal, 3–4 cm long, up to 1.5 cm thick, roots fibrous. Leaves 4–8 basal, clustered at the apex of the rhizome; clearly whorled, orbicular-ovate to triangular, 3–9 × 3.5–11 cm, papery, base cordate, apex rounded, margin irregularly triangular denticulate, upper surface densely covered with eglandular short hairs and sparse long hairs, lower surface sparsely covered with short and long hairs confined to the veins; basal veins 4 or 5, lateral veins 3–4 on each side of midrib, palmate; petioles terete, 2–9.5 cm long, densely covered with fuscous hairs. Cymes 1–4, axillary, 4 to many flowered; peduncle 10–18 cm long, densely covered with brown villous, pedicel 1–2.5 cm long, with same indumentum as on the peduncle. Bracts 2, opposite, subulate to subulate-triangular, ca. 6 mm long, adaxially glabrous, abaxially puberulent, margin sparsely denticulate, densely ciliary villous; bracteoles 2, opposite, subulate, 2–3 mm long, indumentum same as bracts. Calyx actinomorphic, 6–6.5 mm long, shallowly 5-lobed to about two-thirds of the calyx length from the base, lobes equal, ca. 2 × 1.5 mm, apices obtuse, margin sparsely denticulate, inside glabrous, outside white puberulent. Corolla zygomorphic, up to 5 cm; glabrous both inside and outside, pink to magenta, inside with two brightly yellow strips at throat. Tube funnel-shaped to tubular, 1.8–2.2 cm long, inflated in the middle, orifice 1–1.5 cm in diameter, base constricted; limb distinctly 2-lipped, adaxial lip 2-lobed to near middle, ca. 0.6–0.8 × 1.6 cm, obliquely triangular, abaxial lip 3-lobed to base, lobes rounded or oblong, ca. 1.1 × 1.1 cm, more or less equal. Stamens 2, adnate to corolla ca. 2.3 cm above the corolla base; filaments 8–10 mm long, straight, swollen at middle, white, glabrous with glandules on the surface; anthers ca. 2 mm long, white bearded. Staminodes 3, adnate to 1.4–1.8 cm above base of corolla tube, 0.3–0.5 mm long, white, glabrous. Disc annular, ca. 1 mm high. Pistil 3.6–4.3 cm long, densely puberulent; ovary white, ca. 3.3–4 cm long, cylindrical, puberulent; style ca. 3 mm long; stigma 1, terminal, depressed-globose, centrally sunken, undivided, translucent. Capsule purplish-red when young, linear-cylindrical, puberulent, up to 9 cm.

Figure 1. 

Didymocarpus heucherifolius var. gamosepalus A habit B habitat, showing Danxia landscape C cyme with flowers D corolla, showing outside glabrous E bracts and bracteoles F calyx, showing base of calyx connate G opened corolla, showing staminodes H pistil I stigma J stamens.

The specific epithet is derived from calyx 5-lobed from middle to above middle.

Hé è Mín Gàn Cháng Shùo Jù Tái (Chinese pronunciation); 合萼闽赣长蒴苣苔 (Chinese name).

The new variety has so far been found only in the type locality, near Pingyuan County, Meizhou City, Guangdong Province. The landform of the type locality is Danxia landform, which is formed from red-coloured sandstones and conglomerates deposited by sedimentation from lakes and streams from mainly the Cretaceous age. The new variety is locally abundant and grows on moist and shaded rocky faces on the cliff in subtropical evergreen seasonal rain forest. The average temperature of Pingyuan County is about 21.7 °C and the average annual precipitation is over 1 600 mm. Flowering is from February to March.

Didymocarpus heucherifolius var. gamosepalus and the type variety, D. heucherifolius var. heucherifolius, share a number of similar vegetative characters, but the new variety differs from the latter in several morphological features, such as larger flowers and glabrous corolla, calyx base connate, 5-lobed from middle to above middle. A detailed comparison of the diagnostic characters between Didymocarpus heucherifolius var. gamosepalus and other variety of D. heucherifolius is shown in Table 1.

There are nine species and two varieties in Didymocarpus Section Heteroboea, including an unpublished new species: D. lobulatus sp. nov. These species are mostly distributed in Eastern China, of which, more than 50% are distributed in the Zhejiang province (shown in Figure 2). The northernmost species is the D. heucherifolius in Linan County, Hangzhou City, Zhejiang Province, while D. heucherifolius var. gamosepalus is the southernmost species. D. heucherifolius is the most widespread species, which can be found in Danxia, Karst limestone and Granite landscapes. As shown in Figure 2, nine localities are Karst landscape (the green points) and nine localities are Danxia landscape (the red points). The majority of Section Heteroboea species (four species and two varieties) were reported on Danxia landscape.

Figure 2. 

The distribution areas of Section Heteroboea and their Parent material. The different colours represent the different Parent material: red – danxia landscape; yellow – granite landscape; green – karst limestone landscape; nlack – volcanic landscape).