exine

The exine is composed of tectum, columellae, foot layer and endexine.

花粉外由顶盖层、柱状层、底层及外内层所组成。

The exine of pollen wall is of different electron density, the nexine dense and the sexine, comprising tectum, bacules, and foot layer, relatively thin.

花粉的外分为外层和内层，外层包括覆盖层、基粒棒和基足层等三层，内层只包含一层。