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 (poems) This cluster of poems contains a number of images and motifs that are repeated throughout. The most important is probably the Calamus root itself. "Acorus calamus" or Sweet Flag is a marsh-growing plant similar to a cat-tail. Whitman continues through this one of the central images of "Leaves of Grass"--Calamus is treated as a larger example of the grass that he writes of elsewhere. Some scholars have pointed out, as reasons for Whitman's choice, the phallic shape of what Whitman calls the "pink-tinged roots" of Calamus, its mythological association with failed male same-sex love and with writing (see Kalamos), and