Gastrodia agnicellus Hermans & P.J.Cribb, 2020

Hermans, Johan, 2020, GASTRODIA AGNICELLUS, Curtis's Botanical Magazine 37 (3), pp. 385-395 : 392-394

Gastrodia agnicellus Hermans & P.J.Cribb , sp. nov.

Type: Madagascar, Fianarantsoa Prov., near Ifanadiana , c. 800 m, ex Malala, 1999, Hermans 2355 (holotype, K) . Fianarantsoa Prov., Ranomafana, Sept. 2019, Field Observations, Hermans et al. (photographs K) .

DESCRIPTION. A holomycotrophic herb, growing as a humicole or trunk epiphyte at the base of trees, underneath humus and leaf-litter. Rhizome tuberoid, fleshy, horizontal, narrowly obovoid to fusiform, 23–48 × 6–16 mm, subdensely noded, with triangular scale-like bracts along the entire length, densely pilose with long greyish-white hairs at the base of the scales, each rhizome arising from the apex of the previous one, with a narrow stalk c. 10 mm long; roots sparse, glabrous to a little verrucose, 30–100 mm long, c. 2 mm in diameter. Inflorescence 14–35 mm tall; peduncle brown; with 4–6 overlapping tubular sheaths along its length; sheaths dark brown, papery, acute, 2–4 × 1–1.8 mm; floral bracts amplexicaul, similar to the sheaths, acute, 4–5 × 1.6–2.1 mm. Flowers 1–3, terminal, densely racemose, resupinate, c. 11 mm long, 5 mm wide, borne at a right angles to the rachis, campanulate, not opening much, somewhat verrucose – pustulate on the outer surface of the sepals, rugose on the interior, pale brown to grey-brown on the exterior, darker orange brown on the interior, the petals a little paler, lip orange-brown with the disk and callus dark orange, tubercular processes at the column-foot orange-brown, column brown; pedicel and ovary c. 11 mm × 2 mm, the pale brown pedicel lengthening greatly and rapidly after fertilisation; ovary obconical, subtriangular in cross-section, somewhat rugulose. Sepals fused into a gibbose tube for most of their length, overall c. 12 × 16 mm; dorsal sepals, elliptic, emarginate, concave, the apex slightly incurved, 10.5–12.1 × 5.4–5.7 mm, lateral sepals elliptic, obtuse, concave, the apical margin incurved, strongly rugose abaxially in the apical half, 11.5–12.5 × 5.9–6.5 mm. Petals borne on the sepals where they divide, concave, ear-like, broadly ovate, obtuse, the margins slightly thickened, 2.4–3 × 1.8–2 mm. Lip fleshy, articulate but fused to the column foot, horizontal within the perianth tube, 5–6.3 × 2.9–3.2 mm, ovate-navicular, attenuate and decurved towards the tip, the margins thickened, transversally crenate-rugose, base shortly clawed, with a globose verrucose callus on each side where it meets the column foot, a distinct longitudinal raised elliptic ridge towards the apex. Column clavate, 6.5–7.4 mm, with two small triangular stelidia at the apex, rostellum lobes long, incurved, angular, foot incurved, pustulate around the stigmatic surface; anther broadly ovate in outline, 1.3 × 1.1 mm; pollinia 2, granular, on a common viscidium. Fruit erect, pale-brown, 22–35 mm long, the pedicel elevating the capsule, reaching up to 35 cm in length before dehiscence ( fig. 6 ).

DISTRIBUTION. Endemic to SE Madagascar.

HABITAT. Humid evergreen forest, in deep shade underneath leaf litter and humus; 600–850 m.

FLOWERING TIME. August to September: buds are initiated during the cooler and drier season and develop further with the first rains, generally during the beginning of September.

CONSERVATION. The new species has only been recorded from the Vatovavy-Fitovinany region, Fianarantsoa province. One of the sites is within the Ranomafana Protected Area, the extent of occurrence is estimated to be very small and in continuing decline due to habitat destruction caused by fire and agriculture. In addition, Gastrodia require specific mycorrhizal associations for carbon uptake throughout their life cycle ( Martos et al., 2009, 2015a, 2015b). These combined factors are likely to mean that the new species is Endangered.

ETYMOLOGY. The species name refers to the woolly covering on the rhizome, the ear-like petals and also alludes to the name of the botanical artist who brought the new species to life in her drawing.

Figures

Fig. 6. Fully developed fruits of Gastrodia agnicellus on an extended pedicel, Ranomafana, December 2017. Photograph: J. Hermans.