Feather These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular "calamus" (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus). Hatchling birds of some
Acorus calamus β-asarone is 2,4,5-trimethoxycinnamic acid, a derivative which is not a carcinogen. Acorus calamus Acorus calamus (also called sweet flag or calamus, among many common names) is a species of flowering plant, a tall wetland monocot of the family Acoraceae, in the genus "Acorus". Sweet flag is a herbaceous perennial, tall. In habit it resembles the iris, and has given its name to the flag iris, "I. pseudacorus". It consists of tufts of basal leaves that rise from a spreading rhizome. The leaves are erect yellowish-green, radical, with pink sheathing at their bases, sword-shaped, flat and narrow, tapering into a long,