Rhipidocladum arenicolum C.D. Tyrrell & L.G. Clark, 2013

Tyrrell, Christopher D. & Clark, Lynn G., 2013, Three new species of Rhipidocladum (Poaceae: Bambusoideae: Arthrostylidiinae) from South America, Phytotaxa 98 (2), pp. 55-64 : 58

Rhipidocladum arenicolum C.D. Tyrrell & L.G. Clark , sp. nov., Fig 2 .

Type:— PERU. San Martín . Rioja: Low forest over white sands, ca. 1 km above Aquas Verdes along trail to San Pablo , 5°41'14"S 77°37'58"W, 1200 m, 7 July 2002 (fl), J. L. Luteyn, I. Sánchez-Vega, & M. Zapata Cruz 15520 (holotype: USM!; isotypes: ISC!, MO!, NY!, US!) .

Diagnosis:— Rhipidocladum arenicolum differs from R. harmonicum in its smaller culm diameter (5–8 mm), longer branches (57–65 cm), longer (16–23 cm) synflorescences and larger florets (lemmas 18.5–19 mm).

Description:— Culm height unknown; internodes ca. 26 cm long, 5–8 mm diameter, hollow. Culm leaves unknown. Branch complements with 18–25 branchlets, branchlets 57–65 cm long, occasionally rebranching from the base. Foliage leaves 4–6 per flowering branchlet; sheaths 32–54 mm long, abaxially glabrous, margins glabrous; fimbriae 1–3 mm long, stramineous to brown, mostly deciduous; pseudopetioles 4–5 mm long, abaxially glabrous, adaxially puberulent, dark brown; inner ligules ca. 0.5 mm, truncate; blades 7–10 cm long, 13–17 mm wide, L:W ratio 5–6, broadly lanceolate, abaxially and adaxially glabrous, base rounded, apex acuminate, margins smooth. Synflorescences 16–23 cm long, spicate, bearing 6–7(–8) spikelets spaced 20–40 mm apart; rachis at least apically geniculate. Spikelets 4.4–5.0 cm long, comprising 2–3 glumes and 6– 7 fertile florets; rachilla internodes (2–) 4 mm long. Lowest glume ca. 4 mm long, 7-nerved, ovate-lanceolate, apex obtuse, abaxially glabrous, mucronate; upper glumes ovate-lanceolate, apex obtuse, abaxially glabrous, adaxially puberulent: second glume ca. 9 mm long, 7-nerved, mucronate; third glume ca. 11 mm long, 9- nerved, mucronate. Lemma 18.5–19.0 mm long, 13-nerved, ovate-lanceolate, apex obtuse, abaxially glabrous, mucronate. Palea ca. 13 mm long, abaxially glabrous, adaxially scabrous, stramineous. Lodicules 3, the anterior pair ca. 6 mm long, posterior one ca. 4 mm long, lanceolate. Anthers 7–8 mm long. Ovary ca. 1.7 mm long, white. Caryopsis ca. 6.5 mm long, 2 mm wide, fusiform, subterete, glabrous, style base persistent, dark brown.

Distribution and Habitat:— Known only from the type locality, growing in (and possibly endemic to) a white sand forest at 1200 m elevation in northern Peru.

Etymology:— Named for the habitats with white sandy soils where it occurs: aren- = sand, cola = dwelling.

Figures

FIGURE 2. Rhipidocladum arenicolum. A. Culm node with branch complement showing apsidate branching, B. Caryopsis, C. Floret showing persistent rachis internode, D. Branchlet bearing terminal synflorescence, E. Spikelet, F. Gynoecium, G. Node of geniculate synflorescence with pulvinus, H. Anther, I. Foliage leaf ligular area. Illustration by Eric Small based on Luteyn et al. 15520.