Pronunciation: (pi-ras'ti-kē), [key]
—pl. -chies. Bot.
one of a number of seemingly secondary spirals or oblique ranks winding around the stem or axis to the right and left in a spiral arrangement of leaves, scales, etc., where the internodes are short and the members closely crowded, as in the houseleek and the pine cone.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.