What is "soft chess"

Chess \Chess\, n. (Bot.) A species of brome grass ( Bromus secalinus) which is a troublesome weed in wheat fields, and is often erroneously regarded as degenerate or changed wheat; it bears a very slight resemblance to oats, and if reaped and ground up with wheat, so as to be used for food, is said to produce narcotic effects; -- called also cheat and Willard's bromus. [U. S.]

Note: Other species of brome grass are called upright chess, soft chess, etc.