Polygonatum angelicum Floden, 2015

Floden, Aaron J., 2015, Three new Solomon’s Seals (Polygonatum: Asparagaceae) from the Eastern Himalaya, Phytotaxa 236 (3), pp. 273-278 : 275

Polygonatum angelicum Floden , sp. nov. ( Fig. 2 )

Similar to Polygonatum oppositifolium (Wall.) Royle in having opposite to proximally subopposite evergreen leaves, but differs in the leaves being distinctly three veined, glaucous abaxially, and the perigone smaller (1 vs 1.5 cm), distinctly constricted near the middle, wholly white and distinctly verrucose surfaces.

Type:— INDIA. Arunachal Pradesh. East Siang District, above Simong village, 28.679746, 95.082156, 2200–2800 m, perigone white with green lobes, surface distinctly verrucose, stem green, abaxial leaf glaucous, inflorescences 2–4-flowered, 24 May 2014, Floden, Bruggeman, & Prehsler 2765 (holotype, CAL!).

Epiphytic herb. Plant perennial, evergreen. Rhizomes terete, segments ovoid to spherical, ca. 1 cm diameter, roots thick, fleshy. Stems terete, slight angles near leaves; 30–40 cm long; red maculate, red or green, stem arching outward and ultimately pendulous; cataphylls borne 5–10 cm below first leaf, deciduous. Leaves petiolate, 2–5 mm. Leaves opposite, lanceolate, 4–8 cm long, widest near base; base rounded, apex long acuminate to shortly acute or obtuse; reddish in new growth, lustrous, dark olive-green at maturity; glaucous abaxially; midrib and secondary veins prominent, especially when dried. Inflorescences axillary in lower axils; 1–5 flowered; peduncles 1–2 cm, pedicels 1–2 cm, bracteoles minute or absent. Perigone 8–13 mm, surface verrucose, white, constricted near middle, lobes deltoid, reflexed to perpendicular (relative to tube), green. Filaments inserted just proximal of middle, ca. 2–3 mm, extending to apex of anther, terete, sigmoid, papillose from middle to apex, connivent around stigma. Ovary green, ovoid, 2–3 mm; style subequal, not surpassing anthers; included in perigone. Fruit spherical, red. Seeds faceted, ca. 1 mm, covered in a distinctive membrane.

Distribution:— CHINA. Xizang (Tibet), Nyingchi Prefecture at 2400 meters. INDIA. Arunachal Pradesh, East Siang District, Yingkiong to Riutala, common from 2200–2800 meters.

Phenology:—Flowering, May–June, Fruiting, October–December (persisting into June the following season).

Other specimens examined (paratypes):— CHINA. Tibet (Xizang), Nyingchi Prefecture. Medog County. Bomê. 2400 m, 7 August 1980, Eco Highland Room Group 14087 ( PE!) ; INDIA. Arunachal Pradesh, East Siang District, Pemako , s.d., photographed in situ by P. Bruggeman ( CAL!, TENN!) .

Taxonomic relationships:— Polygonatum angelicum is more similar to the following species, P. luteoverrucosum , than either are to P. oppositifolium , despite all three having opposite leaves, seeds covered in a distinctive membrane, and an epiphytic habitat. The perigone of the former two are nearly half the length of P. oppositifolium and they are distinctly constricted near their middle. Moreover, their perigone surfaces are verrucose which is observable without magnification ( Figs. 3 , 4 ). This character is not observed in P. oppositifolium or other species though the surface of some P. cathcartii collections are minutely papillose when viewed at 10× or greater magnification. In addition, these two species do not have reddish maculation on the perigone like P. oppositifolium . Despite the similarities of Polygonatum angelicum to P. luteoverrucosum it can be distinguished by its white-green vs. yellow perigone; the red spotted vs. reddish mature stems; the abaxially glaucous vs. lustrous leaf surfaces; the prominently 3-veined vs. 1-veined leaves, and the long peduncle and few-flowered vs. short and many-flowered inflorescences. In fact, the prominently veined leaves, spotted stem, and the glaucous abaxial leaf surface of P. angelicum are all shared with P. cathcartii occurring at slightly (+ 100 m) higher or barely overlapping elevations. My impressions based on field observations are that P. angelicum may be a species of hybrid origin between P. cathcartii and P. luteoverrucosum because of several morphological characters that are intermediate between the two parents which grow at elevations above and below it, respectively. This hypothesis will need to be tested with molecular data. Notwithstanding the limited number of known collections of Polygonatum angelicum and P. luteoverrucosum they probably share the same extent of distribution. Despite their close proximity, observation of the two species in Arunachal shows they occupy different elevation gradients. The former occupies elevations nearly 400 meters higher than the latter in habitats with apparent differences in floristic components; the former in Rhododendron dominated forests and the latter in subtropical broad-leaved evergreen forest. The description of these two species and observation of specimens reduces the total distribution of P. oppositifolium to two areas: the first from western Bhutan and west into Nepal (from whence the type was collected) where it occurs in adjacent Xizang in Nyalam County; and the second in the Khasia Hills of Assam, the Garo Hills of Meghalaya, and into the foothills of Manipur. The plants in this latter area of distribution occasionally do not have the typical reddish maculation on the perigone ( Gogoi 2010, personal observation), but the surface of the perigone is also not verrucose like P. angelicum or P. luteoverrucosum .

Figures

FIGURE 2. Left, Polygonatum angelicum whole plant, Right, dissected perigone showing the ovary and style length, and the filament insertion and shape. Perigone ca. 1 cm long. Photographed in the field by the author at approximately 2400 meters, Arunachal Pradesh, India.

FIGURE 3. Polygonatum luteoverrucosum photographed in the field by the author at approximately 1600 meters, Arunachal Pradesh, India. Perigone ca. 1 cm long.

FIGURE 4. Polygonatum luteoverrucosum perigone dissected, photographed in the field by the author, showing the insertion point of the filaments and equal ovary and style lengths. Perigone ca. 1 cm long.