螺旋形的

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，羽枝以螺旋管状的羽芽生长，在管子的一侧接合在一起成羽轴，时在管子的另一侧成新的羽枝脊。