Crest (feathers) Crest (feathers) The crest is a prominent feature exhibited by several bird and other dinosaur species on their heads. The crest is made up of semiplume feathers: a long rachis with barbs on either side. These are plumulaceous feathers, meaning that they are soft and bendable. In birds, these semiplumes are common along the head, neck, and upper back, and may be used for buoyancy and sensing vibrations. Crests on birds are generally used for display purposes. Cockatoos and their smaller cousins, cockatiels, are part of the parrot family Cacatuidae found in Australia, the Bismarck Archipelago and the Philippines, and
Acorus calamus asexually. The tetraploid variety is usually known as "Acorus calamus var. angustatus" Besser. A number of synonyms are known, but a number are contested as to which variety they belong. It is morphologically diverse, with some forms having very broad and some narrow leaves. It is furthermore also cytotypically diverse, with an array of different karyotypes. "A. calamus" has been an item of trade in many cultures for thousands of years. It has been used medicinally for a wide variety of ailments, and its aroma makes calamus essential oil valued in the perfume industry. The essence from the rhizome is