Didymocarpus parryorum C.E.C.Fisch., Bull. Misc. Inform. Kew. 1928(4): 142. 1928.

Prasanna, Naibi Shrungeshwara & Gowda, Vinita, 2020, Rediscovery of four narrow endemic Didymocarpus species (Gesneriaceae) from Mizoram, India, with revised species descriptions and lectotypifications, PhytoKeys 148, pp. 1-19 : 1

Didymocarpus parryorum C.E.C.Fisch., Bull. Misc. Inform. Kew. 1928(4): 142. 1928. Fig. 4 , Suppl. material 1: Fig. S1C, E

Lectotype

(designated here). India. Assam (= Mizoram), Lunglei district, Lushai hills at Sairep, 5000 ft., July 1926, Mrs N.E. Parry 7, K (K000820535!).

Lectotypification.

The protologue by Fischer indicates the specimen that was studied for the description of the species as "India. Assam, South Lushai Hills at Sairep, 1700 m. July, Mrs N E.Parry 7 ". During our study we located five different sheets at Kew herbarium having the same collection number and locality as quoted above. Hilliard and Burtt (1995) noted that Parry’s numbers do not refer to individual collections, but instead they refer to unique species that she had recognized in the field. Weber et al. (2000) recognized three of these specimens as type material, but failed to designate a lectotype. One of these specimens, with a barcode number K000820535, has the collector’s original label which mentions 'July 1926' as the collection date. The author’s note on the label matches the note that Fischer has quoted in the protologue: "grows on rocky cliffs, leaves pale-green, silvered when dry, calyx light yellow, corolla orange red". Since this is the only specimen where the collection number, month, and the author’s note matches the protologue, we designate K000820535 as the lectotype here.

Revised description.

Terrestrial or epilithic herbs, up to 20 cm tall, total height including inflorescence ca. 25 cm. Rhizome 1-2 × 0.5-1.0 cm. Stem 3-10 × 3.5-8 mm, erect, dark brown to light green, terete, pubescent with eglandular hairs, interspersed with yellowish cruciform pigment glands (in dried specimen). Leaves 1 - 4 pairs, opposite, anisophyllous, decussate, arrangement tufted in close pairs, terminal pair is reduced, exstipulate; petioles 4-9 cm long, light brown to light green, pubescent as on stem, interspersed with yellowish cruciform pigment glands (in dried specimen); lamina 6-12 × 5-10 cm, orbicular to ovate, base cordate to obliquely cordate, apex acute to subobtuse, margins crenate to serrate, dorsal surface dark green, pubescent with eglandular hairs, ventral surface light green, veins pubescent and intervals sparsely pilose, hairs eglandular, abaxial surface is covered with yellow to brownish cruciform pigment glands (in dry specimen); midrib with 6-8 secondary veins in either side, basal 3-4 pairs palmate, sunken above, raised below. Inflorescence 1-4, pedunculate, erect, axillary, pair-flowered dichasial cymes, arising from the axils of the 1-2 uppermost pairs of leaves, cyme with 12-16 flowers; primary bracteoles present, 8 × 4 mm, greenish-yellow, opposite, ovate, apex subacute, glabrous, abaxial surface covered with small cruciform pigment glands, secondary bracteoles yellow, present at the base of each cyme unit, 6 × 3 mm, thick, veins visible in dried specimens; orange flowers contrast against yellow calyces; peduncle 10-25 cm long, up to 2 mm wide, brownish at the base, light green towards apex, pubescent with eglandular hairs, sparsely covered with minute cruciform pigment glands as on bracteoles; pedicel 4-12 mm long, greenish-yellow, glabrous, pigment glands absent. Calyx up to 1 cm long, bright yellow, linear lanceolate, apex acute, lobes 5, free to base, conspicuously veined, glabrous, thick, persistent. Corolla 1.3-2.2 cm long, ca. 1.5 mm wide, tubular, tip infundibuliform, glabrous, corolla tube dorsally orange while ventral section of the corolla tube with a light yellow stripe running along the length of the tube, corolla lobes bilabiate, orange, glabrous, orbicular, upper lobes 2, 1.5 × 2 mm; lower lobes 3, 4 × 3 mm, spreading at right angles to the upper lobes, central lobe wider than the 2 lateral lobes. Stamens 2, oblong, glabrous, inserted near the throat of the corolla tube, anthers dorsifixed, coherent by adaxial surfaces; filaments 4-5 mm long, yellowish orange, glabrous; staminodes 2, 2 mm long, linear. Disc up to 1.2 mm, tubular with undulating upper margin, yellowish, glabrous, persistent. Gynoecium ca. 2 cm, ovary greenish yellow, linear, glabrous; style ca. 0.5 cm, glabrous; stigma capitate, green. Capsules 17-24 mm, linear, glabrous, orthocarpic. Seeds minute, ellipsoid, glabrous, muricate.

Amendments to protologue.

Upon examining the historical specimens and our fresh collections (Fig. 4 ) we believe that the indumentum on the stem is better described as pubescent rather than as strigose. Similarly, we describe corolla lobe shape as orbicular and not suborbicular (as mentioned in the protologue).

Note.

Differs from D. tristis Craib in having larger, bright yellow colored bracteoles and sepals respectively (maroon bracteoles and sepals in D. tristis ). In addition, D. parryorum has orbicular to ovate leaves (oblong to lanceolate in D. tristis ) and smaller corolla (1.3-2.2 cm in D. parryorum , 2-2.4 cm in D. tristis ).

Distribution and vernacular name.

Historically, D. parryorum is known from only two districts (Lunglei and Lawngtlai) of southern Mizoram. We could locate the species only from the type locality (Sairep village in Lunglei district, specimen numbers: VG2018MZ2522, VG2018MZ2528, VG2018MZ2529, VG2018MZ2546). In Sairep, the plant is known as ' Chhakzhau ' in local Mizo language.

Habitat.

This plant is generally found growing on moist loamy banks in partially shaded tropical wet evergreen forests.

Phenology.

Flowering in July to September, fruiting in August to December.

Conservation status and preliminary IUCN assessment.

Didymocarpus parryorum is historically known from only two localities in southern Mizoram, India: Lunglei and Lawngtlai districts. It has not been collected for the past 90 years, until this study in 2018, when we found it growing in its type locality. The extant population is restricted to a small patch of less than 10 km2 in a rapidly degrading forest and it has about 500 mature individuals. A village road passes through the plant’s habitat, further threatening its population. Therefore we propose that the species should be considered as critically endangered (CR) as per the B2ab criteria of IUCN guidelines ( IUCN 2019).

Figures

Figure 4. Didymocarpus parryorum C. E. C. Fisch. A habitat B habit C complete plant with inflorescence D inflorescence E floral dissection from left to right: primary bracteoles (above), secondary bracteoles (below), corolla tube, calyx with gynoecium, open floral tube with anther (fusion of anther lost in dissection of flower) F mature fruit G glands on the lower surface of leaves. Photographs by NSP.