Abstract: The genus Acidosasa was published by the present authors in 1979. It only had one species at that time, Acidosasa chinensis C. D. Chu et C. S. Chao. Since then species number of the genus steadily increases. The authors have rather comprehensively studied this genus and its related genera for F1. Reip. Pop. Sin. The present paper deals mainly with morphological characteristics of the genus Acidosasa and the differences from its related genera i. e. Arundinaria, Sasa and Indosasa. The genus Acidosasa is closely related to the genus Arundinaria in the type and origin of inflorescences and the vegetative appearance. But it differs from Arundinaria in the structure of florets. In Acidosasa, each floret is provided with six stamens, while in Arundinaria each floret is of only three stamens. The genus Acidosasa is similar to the genera Indosasa and Sasa in the numbers of stamens, but it is distinguished from lndosasa by its semelauctant (determinate) inflorescence, not iterautant (indeterminate) one, from Sasa by its taller stature and branch complement with three branches. We have carefully examined all the type specimens of Acidosasa and its related genera. A conclusion reached is that there are six species in the genus Acidosasa, most of which are native to S. China, with only one species in Viet Nam. Five specific binomials are reduced and one species is transferred into this genus. Two keys to species, respectively based on the flowering and vegetative characters, are given as follow: Key to species of the genus A cidosasa (1)(based on the flowering state) 1. Lemmas glabrous. 2. Spikelets stout, 3-6mm broad, pedicels 1.5-4cm long; lemmas large, 1.5-2.2cm long, with 15-19 nerves, subcoriaceous, not glaucous, shiny. 3. Lemmas up to 2.2cm long with conspicuously transverse veinlets, tessellate; palea and rhachilla entirely. glabrous, lodicules elliptic-lanceolate, glabrous ... 1. A. chinensis 3. Lemmas 1.5-1.8cm. long, slightly tessellate; palea puberulous at apex of carina, rhachilla puberuous at apex, lodicules obovate, ciliate at apex ............ 2. A. brilletii 2. Spikelets rather slende, 2-4mm broad, pedicels 0.5-1cm long; lemmas small, about 1.3 cm long, with 7-13 nerves, more or less glaucous .......... 3. A. chienouensis 1. Lemmas pubescent. 4. Glumas and lemmas densely pubescent ........................ 4. A. hirtiflora 4. Glumas subglabrous, lemmas sparsely pubescent. 5. Spikelets large, 3-7 cm long, lemmas 1.6-1.7 cm long, pedicels 2-13 mm long ................................................. 5. A. longiligula 5. Spikelets small, 2-3.7 cm long, lemmas about 1.3 cm long, pedicels 1-3 cm long ................................................... 6. A. venusta Key to species of the genus A cidosasa (2) (based on the vegetative state) 1. Ligules of leaf-sheaths strongly elevated, usually 2-8 mm long. 2. Young culms with bristly sheath scars; culm-sheaths without auricles and oral setae, not spotted, sheath-blades erect ................. 4. A. hirtiflora 2. Young culms with glabrous sheath scars; culm-sheaths with small auricles and oral setae, sparsely spotted, sheath-blades reflexed .......... 5. A. longiligula 1. Ligules of leaf-sheaths inconspicuous, less than 2 mm long. 3. Young culms more or less bristly, or sheath-scars bristly: 4. Culm-sheaths without auricles and oral setae, not farinose, without hairs at base. 5. Young culms densely bristly; culm-sheaths attenuate at apex and as wide as sheath-blades, with conspicuously transverse veinlets; leaf-blades large, usually 2.5-3.5 (-6.5) cm broad, conspicuously tessellate ..................................................... 1. A. chinensis 5. Young culms sparsely bristly; culm-sheaths truncate at apex and broader than sheath-blades, without transverse veinlets or inconspicuous; leaf-blades small, 1.5-2.5 cm broad, without visible transverse veinlets .................................................... 6. A. venusta 4. Culm-sheaths with auricles and oral setae, slightly farinose, densely bristle at base; leaf-blades rather narrow, 0.8-1.8 cm broad ............ 3. A. chienouensis 3. Young culms entirely glabrous; leaf-blades rather narrow, 1.2-1.8 cm broad ....................................................................................... 2. A. brilletill

Key words: Acidosasa, Taxonomy.