Feather development grows, its spathe, which is where the rachis and vanes attach, continues to form. When spathe is finished developing, the calamus begins to form within the base of the spathe. The calamus is the quill of the feather, which is the bottom portion that stays mainly within the pulp cavity. From there, the feather is fully developed and will remain as such until molting occurs, causing it to fall off. Feathers fall off during molting, which occurs in the at different times through the year depending on the type of bird. Birds can molt for seasonal, reproductive and many other
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