主枝

1.The two halves of the main branch have grown apart.

主枝两边各向不同方向生长。

2.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.

而不论是何种羽毛，羽枝主枝延伸出来羽小枝，都羽枝脊表面叫做「羽小枝板」单层细胞长出来。