Arthrostylidium simpliciusculum ( Pilger 1920: 29 ) McClure (1973: 20)

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, Phytotaxa 550 (2), pp. 99-129 : 107

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.

Figures

FIGURE 2. Field photographs of bamboos from Serra do Cachimbo. A–C. Actinocladum verticillatum: A–B. Habit. C. Culm leaves. D–I. Arthrostylidium simpliciusculum: D. Habit. E. Branch complement. F. Culm leaf sheath margins. G. Culm leaf apex. H. Foliage leaf complement. I. Foliage leaf fimbriae. J–N. Eremocaulon capitatum: J. Habit. K. Infra- and supranodal bands of trichomes and culm leaves. L. Foliage leaf fimbriae. M. Synflorescence. N. Pseudospikelets. O–R. Guadua paniculata: O. Habit. P. Infra- and supranodal bands of trichomes and thorns. Q. Foliage leaf complement. R. Culm leaves. Photos: P.L.Viana (A–K, M–O, R) and M.Pastore (L, P).