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
Rachis achieved pachytene and are attached to the walls of the gonadal tube. The rachis is filled with cytoplasm. In plants, a "rachis" is the main axis of a compound structure. It can be the main stem of a compound leaf, such as in "Acacia" or ferns, or the main, flower-bearing portion of an inflorescence above a supporting peduncle. A ripe head of wild-type wheat is easily shattered into dispersal units when touched or blown by the wind. A series of layers forms that divides the rachis into dispersal units consisting of a small group of flowers (a single spikelet) attached