Arthrostylidium simpliciusculum McClure 1973
Creators: name: Lopes-Neto, Raimundo Balieiro
name: Viana, Pedro Lage
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Poales
Poaceae
Arthrostylidium
Arthrostylidium simpliciusculum

description: Arthrostylidium simpliciusculum (Pilger 1920: 29) McClure (1973: 20)
≡ Arundinaria simpliciuscula Pilger (1920: 29). Fig. 2 D–I.
Type:— BRAZIL. Amazonas: Manaus, Pensador bei Manaus, Ule 8813 (holotype B, isotype US).
Rhizomes pachymorph, necks 2–3 cm long. Culms ca. 5 m tall, 2–3 mm in diameter, erect at first and later scandent, clambering in trees and later pendent, internodes 30.5–37.7 cm long, hollow, scabrous when young, smooth at maturity; primary buds subequal, prophyll unitary, 6.3–8.2 × 2.3–3.8 mm, glabrous, margins ciliate; nodes brown, glabrous, horizontal, supranodal ridge inconspicuous. Branch complement with 15–17 subequal, widely spreading branches, ca. 24 cm long, ca. 1 mm in diameter, internodes 5–8 cm long. Culm leaves persistent or tardily caducous, green when young, stramineous at maturity; sheath 3.4–4.5 × 1–2 cm, confluent with the blade, glabrous on both surfaces, margins densely ciliate, with white trichomes; auricles absent; fimbriae ca. 0.5 mm long, erect, hyaline; inner ligules ca. 0.1 mm long, symmetrical, membranous-ciliate; blades 2.5–2.8 × 1–2 cm, triangular-lanceolate, glabrous on both surfaces, margins densely ciliate, with white trichomes, apex setose, tip 5–6 mm long. Foliage leaves 4–8 per complement; sheaths 2.3–3.6 × 2 cm, greenish, glabrous on both surfaces, one margin glabrous and the other minutely pubescent; auricles absent; fimbriae ca. 5 mm long, straight at the base and sinuous toward the apex, ochraceous; inner ligules ca. 0.1 mm, symmetrical, membranous; outer ligules ca. 0.1 mm, asymmetrical, rim-like form, membranous; pseudopetioles 1.2–2.2 mm, flat, glabrous or shortly pubescent; blades 10–14 × 0.5–1 cm, lanceolate, glabrous on both surfaces, except 1–2 scabrous marginal nerves, 11-nerved, midnerve central, base obtuse, margins scabrous, densely scabrous at the apex, apex acuminate. Synflorescences not seen.
Specimens examined: — BRAZIL. Pará: Altamira, Reserva Biológica Nascentes da Serra do Cachimbo, Cachoeira do Curuá, ca. 400 m da BR- 163, 368 m, 8°44’08.3”S, 54°57’43.6”W, 30 September 2019, Pastore et al. 1166 (MG); ibidem, 28 May 2021, Lopes-Neto et al. 772 (MG).
Distribution and habitat: —This Amazonian species is found in Brazil, Colombia, Ecuador and Peru (Judziewicz & Clark 1993, Vorontsova et al. 2016). In Brazil, it is registered in Amazonas state (Viana 2020) and this is the first record for Pará state. This species occurs in wet lowland forests at elevations from 30 to 300 meters (Judziewicz & Clark 1993). In the Serra do Cachimbo, it was found in Open ombrophilous forest, along the Curuá rivers margins.
Comments: — Arthrostylidium simpliciusculum is the only species of the genus with the lemma midnerve prolonged into a scabrous awn 1.5–3(5) mm long (Judziewicz & Clark 1993). It can be recognized by the culm leaf margins ciliate, with whitish trichomes, summit sparsely fimbriate, ca. 0.5 mm long, blades triangular-lanceolate, apex setose, tip 5–6 mm long and foliage leaf sheath glabrous except minutely pubescent at one margin, fimbriae ca. 5 mm long, ochraceous, and blades 10–14 × 0.5–1 cm, lanceolate, and glabrous on both surfaces, except 1–2 scabrous marginal nerves. To distinguish this from Arthrostylidium cachimboense, see comments under that species.
description: Published as part of Lopes-Neto, Raimundo Balieiro & Viana, Pedro Lage, 2022, Flora of the Serra do Cachimbo (Eastern Amazon, Brazil): Bambusoideae (Poaceae), including the description of two new species, pp. 99-129 in Phytotaxa 550 (2) on page 107, DOI: 10.11646/phytotaxa.550.2.2, http://zenodo.org/record/6641088