Polygonatum autumnale Floden, 2015

Floden, Aaron J., 2015, Three new Solomon’s Seals (Polygonatum: Asparagaceae) from the Eastern Himalaya, Phytotaxa 236 (3), pp. 273-278 : 273-274

Polygonatum autumnale Floden , sp. nov. ( Fig. 1 )

Similar to Polygonatum gongshanense L.H.Zhao & X.J.Xe. in that the filaments have a retrorse spur, also similar to P. cathcartii Baker (1875: 559) in having opposite leaves, but differs from both in the obtuse leaf apices, the pink-maculate perigone, the distinctly distally-inflated perigone tube, and by its autumnal flowering period.

Type:— INDIA. Arunachal Pradesh, Lower Dibang District, Mayodia Pass, 28.238727, 95.939444, 2700 meters, growing on tree trunks and rocks with Pleione hookeriana , pressed from a cultivated specimen, 18 September 2014, P. Bruggeman s.n (holotype, CAL!).

Epiphytic herb. Plant perennial, evergreen. Rhizomes moniliform, segments spherical, 0.5–2 cm diameter, roots thick, fleshy. Stem terete, 20–30 cm long; purple tinted, red-maculate or occasionally all green, stem pendulous; cataphyll borne below the first leaf pair, deciduous. Leaves opposite, lanceolate, 4–7 cm long, widest near the base; base rounded, apex obtuse; purple tinted in spring, green at maturity, glaucous abaxially, papillose at 20× magnification. Inflorescences axillary in lower axils, occasionally all along the stem; 1–2-flowered; peduncles 1–2 cm, pedicels 1–1.5 cm, distinctly articulate proximally, red maculate; bracteoles attached at articulation, subulate and caducous. Perigone 1.6–2 cm, inflated distally, distinctly tapered to ovary and urceolate constricted at mouth; white with heavy pink maculation on the outer surface; lobes green. Filaments inserted near mouth of perigone, flattened sigmoid with a retrorse spur (facing perigone tube wall) oriented perpendicular from the anther to the widest point in perigone tube, surface papillose, connivent around stigma. Ovary greenish, ovoid, 1–3 mm long; style 1.6–1.9 cm long, exerted from mouth of perigone. Fruit ovoid, 5–8 mm, ripening to orange-red. Seeds ovoid, surface rugulose ca. 1 mm.

Etymology:—Named for its flowering period which is the only known autumn-flowering species of Polygonatum .

Distribution:— INDIA. Arunachal Pradesh; Lower Dibang District, Mayodia, near pass at ca. 2700 m.

Ecology:—Epiphytic or lithophytic, growing in thick bryophyte mats in sub-temperate rainforest.

Phenology:—Flowering, September–October, Fruiting, May–June.

Notes:—At the only known locality it grows in a sheltered portion of the ridgeline, but it is sympatric with two other Polygonatum ; P. cathcartii and an unidentified species which both grow terrestrially on adjacent slopes of the ridge at lower and higher elevations, respectively. Both sympatric species have opposite or occasionally also threewhorled leaves, respectively, though they are spring-flowering and are deciduous.

Taxonomic relationships:—Morphological comparisons of Polygonatum autumnale reveal it to be similar to the recently described P. gongshanense , but it differs in its autumn-flowering period, its white perigone with pink maculation and the purple new growth. Zhao and Xe (2014) compared P. gongshanense to P. cathcartii which is also sympatric here with P. autumnale , but differs in the filament shape, leaf venation, and habitat (epiphytic vs terrestrial). All three share opposite phyllotaxy and glaucous abaxial leaf surfaces, but P. cathcartii does not have the retrorse spurs on the surface of the staminal filaments. More importantly, P. cathcartii is deciduous and P. autumnale is green in winter, but it remains unknown whether it is summer dormant after fruit maturation. Zhao and Xe (2014) did not mention whether P. gongshanese was deciduous.

Figures

FIGURE 1. Images of Polygonatum autumnale: left, perigone dissected on a grid with 5 mm gridlines showing the insertion level of the filaments, their distinctive spurs, the long exerted style, and the pink-maculate coloration, photo P. Bruggeman; right-top, plant in field in fruit showing the articulate pedicels and ovoid immature fruit, taken by the author May 2014; right bottom, plant in flower in the field September 2013, photo P. Bruggeman.