In a pennaceous feather, the barbs grow helically around the tubular feather germ and fuse on one side to form the rachis.Simultaneously, new barb ridges form on the other side of the tube.

在正羽上，羽枝以螺旋形绕著状羽芽生长，在一侧接合在一起形成羽轴，同时在另一侧形成新羽枝脊。