The seed of wild Emmer Wheat keeps its attached protective scales when it drops to the ground. These scales have bristles (awns) at the tips which cultivate the seed by propelling it mechanically into the soil.
During a period of increased humidity in the night, the awns of the seed capsule become erect and draw together, in the process pushing the seed into the soil. In the daytime the humidity drops and the awns slacken back again; fine silica hairs act as hooks in the soil to prevent the seed from reversing back out again.
During the course of alternating stages of daytime and night time humidity, the awns pumping movements, which resemble the kick of a swimming frog, drill the seed as much as an inch into the soil.
When Sweet Vernal grass seeds are put on a moistened hand, they will move about like little insects from the uncoiling of the spiral twist of the awns.
It is a party trick with one species to put the seed in the palm of the hand and watch it travel up your sleeve and end up at the armpit.
Some awns can be deadly to animals. One species of grass is known as ‘Rip Gut’, an annual Brome naturalised in many countries. The awns are 2″ long, very sharp and very rough due to tiny barb-like hairs that face backwards. This enables the seed to catch and lodge like a fish hook. They can then drill themselves into animal bodies and cause festering sores.