Arthrostylidium Ruprecht (1840: 117)

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 : 104

Arthrostylidium Ruprecht (1840: 117) .

TYPE:— Arthrostylidium cubense Ruprecht (1840: 118) .

Plants cespitose. Culms homomorphic, generally scandent or clambering, less commonly erect, 3–15 m tall, infra-and supranodal bands of trichomes absent. Branch complement consisting of 3-many branches borne on a promontory, without thorns. Culm leaves and foliage leaves clearly distinct. Culm leaves not clearly differentiated along the culm, with erect blades, confluent with the sheath, sheaths fimbriae present, sometimes absent. Foliage leaf sheaths with fimbriae at the apex, translucent swelling absent, outer ligule present, blades linear to lanceolate or less commonly elliptical, midnerve not prominent. Synflorescences terminal to leafy, determinate, a spicate raceme lacking bracts, rachis straight, flexuous or strongly zigzag; spikelets subsessile, bisexual, glumes 1–2, 1 to many-flowered, anthecium smooth (as far as known). Fruit a basic caryopsis, hilum long-linear.

Arthrostylidium is a polyphyletic genus of woody bamboo with thirty-two species in Central and South America ( Kellogg 2015, Tyrrell et al. 2018, Clark et al. 2020, Ruiz-Sanchez et al. 2021). It is distinguished by the branch complement on a promontory and culm leaves with erect blades ( Judziewicz & Clark 1993). In Brazil, four species occur in the Amazon ( Viana 2020). In the Serra do Cachimbo, it is represented by two species, of which one is a new taxon here described.

Identification key to the species of Arthrostylidium from the Serra do Cachimbo, Eastern Amazon, Brazil.

1. Culm leaf blades 21–24.2 cm long, lanceolate, scabridulous with yellowish trichomes at the base of the adaxial surface, apex acuminate; foliage leaf auricles present, 1–2 mm long, blackish, fimbriae 9–11 mm long, copperish, blades 25–26 × 4.4–4.8 cm, broad-lanceolate .................................................................................................................................. Arthrostylidium cachimboense

- Culm leaf blades 2.5–2.8 cm long, triangular-lanceolate, glabrous, apex setose, tip 5–6 mm long; foliage leaf auricles absent, fimbriae ca. 5 mm long, ochraceous, blades 10–14 × 0.5–1 cm, lanceolate ................................... Arthrostylidium simpliciusculum