Rye Brome

Barry Stewart tipped me off about a population of Rye Brome (Bromus secalinus) in an arable field of wheat near Margam. It's a grass and it may not raise eyebrows, but it is very distinctive and Barry's discovery provides a notable, new record for NPT.
Rye Brome is an archaeophyte (an alien introduced into the British Flora before AD 1600) and was  probably brought to Britain in ancient times mixed with cereal crop seeds, particularly wheat and rye. Until the introduction of efficient seed cleaning methods, the seeds of Rye Brome were common contaminants of cereal crops. Rye Brome is good at doing this. It  has evolved to mimic the cereal crops with which it grows, so that the spikelets that contain the seeds (or grain) disarticulate (break up) and release the seed at exactly the right time to ensure collection with the cereal harvest. The seeds of Rye Brome are also very similar in size to cereal grain, so they are not very conspicuous contaminants. Not surprisingly, Rye Brome became a very successful arable weed and,occasionally, Rye harvests contained so much contaminating seed that the flour was spoiled by a characteristic bitter taste. Before people knew better, this was thought to have resulted from a degeneration of the Rye crop itself. According to Cope & Gray (in Grasses of the British Isles), this is where the name Cheat Grass originated. With the advent of efficient seed 'cleaning', Rye Brome became less common as an arable weed and decreased greatly in abundance. It seems to be making something of a comeback for some reason.