1. The outer layer of the wall of a pollen grain or spore.
Usage: technical; botany

Examples

• The exine of the pollen grain is often ornamented with spines or ridges.
• Botanists examine the exine under a microscope to identify plant species.
• The thickness and texture of the exine vary greatly among different plant families.
• Pollen grains are protected by a tough exine layer that resists decay.
• The exine's distinctive patterns help paleontologists study ancient plant life.