Identification key to Bromus known from along the coastline between the localities of Mar Chiquita and Quequén, Argentina

1. Spikelets slightly rounded, never flattened laterally; lemmas rounded on the back, awns shorter to longer than the lemma, inserted greater than or less than 1.5 mm below the lemma apex................................................................................................................... 2

- Spikelets strongly flattened laterally, lemmas carinate; awns shorter than the length of the lemma, sometimes reduced to a sharp point, inserted less than 1.5 mm below the lemma apex ( Bromus sect. Ceratochloa).......................................................................3

2. Plants annual, without rhizomes; lower leaf sheaths pubescent; lower glume 1-nerved, 15–21 mm long; upper glume 3–5 nerved, 22–32 mm long; lemmatal awn 30–55 mm long; spikelets 3–8-flowered ( Bromus sect. Genea) ....................................... B. rigidus

- Plants perennial, with short rhizomes; lower leaf sheaths slightly pubescent, lower glume 3-nerved, 7–12 mm long; upper glume 5-nerved, 9–13 mm long; lemmatal awn (1–) 3–7 mm long; spikelets 5–12(–16)-flowered ( Bromus sect. Bromopsis) ..................... ........................................................................................................................................................................................... B. auleticus

3. Plants annual to briefly perennial; leaf blades glabrous to pubescent; lower glume 5–11 mm long, upper glume 6.5–13 mm long; lemma 9–13 nerved; inflorescence an open panicle, somewhat pyramidal, with branches away from the main axis ........................ ............................................................................................................................................................ B. catharticus var. catharticus

- Plants perennial; leaf blades pubescent; lower glume 8–15 mm long, upper glume 9–17 mm long; lemma 7–9 nerved; inflorescence an open elliptic-pyramidal panicle, semi-contracted, with branches close to the main axis.............................................. B. alonsae