Raddiella Swallen (1948: 89) .

TYPE:— Raddiella nana (Döll 1877: 329) Swallen (1948: 89) .

Plants delicate, tufted, forming low mats. Culms homomorphic, commonly decumbent, 1–40 cm tall, infra-and supranodal bands of trichomes absent, unbranched or branched, without thorns. Leaves not differentiated into culm leaves and foliage leaves. Leaf sheaths without fimbriae at the apex, translucent swelling absent, outer ligule absent, blades ovate-triangular or elliptical, midnerve not prominent. Synflorescences terminal and axillary, racemose, terminal synflorescence with male and female spikelets or more commonly strictly male, rarely female, axillary synflorescences barely exserted from the leaf sheaths; spikelets with filiform pedicels, solitary and unisexual, glumes 2 (female spikelets) or absent (male spikelets), anthecium smooth. Fruit a basic caryopsis, hilum punctiform or shortlinear, ca. ½ the length of caryopsis.

Raddiella is an herbaceous bamboo with eight species in Central and South America (Kellogg 2015). It is mainly characterized by the decumbent culms, 6–40 cm tall, leaves ovate-triangular or elliptic and synflorescences racemose, terminal and axillary, with male and female spikelets usually arising from different synflorescences (Zuloaga & Judziewicz 1991). In Brazil, five species occur in the Amazon, Caatinga, Cerrado and Mata Atlântica domains (Oliveira & Oliveira 2020). In the Serra do Cachimbo, it is represented by three species.

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

1. Leaf blades elliptical, symmetrical, base and apex acute, short-pilose on both surfaces or scabrous on the abaxial surface; female spikelets falling entire......................................................................................................................................... Raddiella malmeana

- Leaf blades ovate-triangular, asymmetrical, base truncate, apex acute, apiculate or short-apiculate, glabrous or short-pilose near the base on the adaxial surface, to densely puberulent on both surfaces; female spikelets with persistent glumes ..........................2

2. Culms 8–40 cm tall; blades 1.5–1.8 cm long; axillary synflorescences bearing male and female spikelets ....................................... ............................................................................................................................................................................ Raddiella esenbeckii

- Culms 3–6 cm tall; blades 0.4–0.6 cm long; axillary synflorescences bearing only female spikelets.................... Raddiella minima