Awns that bore seeds into soil

Dry: the awn twists 🍂 Cooke says drying bends the awn at a right angle to the narrow carpel and twists it into several turns.

Moisture reverses the twist 💧 In moist air or when wet, Cooke says, the awn untwists.

The turn bores the fruit in 🌱 On loose soil, Cooke reports, awn sweeps rotate the carpel and drive its sharp end down, burying the seed-bearing end.