spiricle

from The Century Dictionary.

• noun In botany, one of the delicate coiled threads in the hairs on the surface of certain seeds and achenes, which uncoil when wet. They probably serve in fixing small and light seeds to the soil, in order that they may germinate.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) One of certain minute coiled threads in the coating of some seeds. When moistened these threads protrude in great numbers.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun botany One of certain minute coiled threads in the coating of some seeds.