Plants annual; tufted. Culms to approximately 50 cm, erect or geniculate, not woody. Sheaths open; ligules membranous, ciliate; blades broadly linear. Inflorescences terminal, panicles of spikelike branches, exceeding the upper leaves; branches 1.5-10 cm, subdigitate or in whorls along elongate rachises, axes flattened, with imbricate, subsessile spikelets, terminating in a rudimentary spikelet. Spikelets laterally compressed, with 3-25 florets; disarticulation of the spikelets below the glumes, of the lemmas within the spikelets acropetal, spikelets falling wholly or in part after only a few lemmas have fallen, paleas persistent. Glumes 1-veined, keeled, exceeded by the florets; lemmas 3-veined, strongly keeled, firmly membranous to cartilaginous, glabrous, cuspidate or awn-tipped. Fruits modified caryopses, pericarp hyaline, rupturing at maturity; seeds deeply sulcate, ornamented. x = 9. Name from the Greek akros, at the tip and achne, scale, referring to the inflorescence branches which terminate in an aborted spikelet (Clifford 1996).