Bromus interruptus, commonly known as the interrupted brome, is a flowering plant in the grass family. It is endemic to southern and central England, which became extinct in the wild in 1972. After several decades in cultivation, the interrupted brome was re-introduced to Aston Rowant National Nature Reserve in 2004, marking the first known re-introduction of an extinct plant in Britain. The plant was a weed of waste places and arable agriculture, particularly of sainfoin (Onobrychis viciifolia) cultivation. It can be distinguished from all other Bromus species by its deeply split, or bifid, palea. The plant appeared to spread rapidly after its discovery in 1849, which is normally indicative of introduced species. However, the species is thought to have arisen in the 19th century as a new species through a substantial and abrupt genetic change. It is thought to have gone into decline with the replacement of horses by motor vehicles from the late 19th century onwards, reducing the demand for sainfoin as fodder, and additionally by improved seed cleaning methods. Description Bromus interruptus is an annual or biennial herb. Its slender to somewhat stout culms measure 20 to 100 cm and occur as either loosely tufted or solitary. They are erect, very lightly pubescent, unbranched and contain 2 to 4 nodes. The green leaves measure 6 to 20 cm long by 2 to 6 mm wide and are long-linear in shape with a pointed apex. They are covered in a soft pubescence. The leaf sheaths are tubular with the lower portion having a soft pubescence replaced by shorter hairs in the upper portion. The ligules measure 1 to 2 mm and are membranous and toothed. The inflorescence is a dense, oblong panicle that measures 2 to 9 cm in length and up to 20 mm thick. It is erect, greyish green in colour and, as the name suggests, usually interrupted, sometimes even reduced to a single spikelet. Its branches measure up to 15 mm in length. The sessile (i.e. without a stalk) or nearly sessile spikelets occur in dense clusters with each measuring 10 to 15 mm long by 5 to 8 mm broad. They are covered in soft pubescence and are plump with a broadly ovate (i.e. egg-shaped) to broadly oblong shape. Each contains 5 to 11 flowers and they slowly break up beneath each lemma once mature. The glumes, or sterile husks at the base of each