Intine

noun

1. The innermost wall of a spore or pollen grain.
2. In botany, the inner coat of the shell of the pollengrains in phenogamous plants, of the spores of fungi, etc. It is a transparent, extensible membrane of extreme tenuity.
3. A transparent, extensible membrane of extreme tenuity, which forms the innermost coating of grains of pollen.
4. The innermost wall of a spore or pollen grain