主枝

The two halves of the main branch have grown apart.

主的左右两边各向不同的方向生长。

In both types of feather, the barbules that extend from the barb ramus grow from a single layer of cells, called the barbule plate, on the periphery of the barb ridge.

而不论是何种毛，主延伸出来的，表面叫做「板」的单层细胞长出来。