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
Calamus rotang Calamus rotang Calamus rotang is a plant species native to India, Sri Lanka and Myanmar (Burma). It one of the scandent (climbing) rattan palms used to make Malacca cane furniture, baskets, walking-sticks, umbrellas, tables and general wickerwork, and is found in Southwest Asia. The basal section of the plant grows vertically for 10 metres or so, after which the slender, tough stem of a few centimetres in diameter, grows horizontally for 200 metres or more. It is extremely flexible and uniform in thickness, and frequently has sheaths and petioles armed with backward-facing spines which enable it to scramble over other