# Costule

**Source**: https://eflora.sydney.edu.au/glossary/costule
**Parent**: https://eflora.sydney.edu.au/glossary/

the mid-[vein](https://eflora.sydney.edu.au/glossary/vein "the vascular bundles of a leaf.") of a [pinnule](https://eflora.sydney.edu.au/glossary/pinnule "the ultimate segment of a divided pinna.") or [segment](https://eflora.sydney.edu.au/glossary/segment "each subdivision of a divided or dissected leaf;") of lesser [order](https://eflora.sydney.edu.au/glossary/order "a taxonomic group of related families."), except the central [vein](https://eflora.sydney.edu.au/glossary/vein "the vascular bundles of a leaf.") of an ultimate [segment](https://eflora.sydney.edu.au/glossary/segment "each subdivision of a divided or dissected leaf;") which is usually called the [midrib](https://eflora.sydney.edu.au/glossary/midrib "the principal vein which runs from the base to the apex of the leaf.") or mid-[vein](https://eflora.sydney.edu.au/glossary/vein "the vascular bundles of a leaf.").

## Related terms

- [Pinnule](https://eflora.sydney.edu.au/glossary/pinnule)