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.
Bird feathers have highly water-resistant parts called the pennaceous barb, which stops the water from actually going in and soaking the rest of the bird.
上，
旋形绕著管状的
合在
有高度防水的部
，叫做羽状倒钩，
