What is a Follicle?
A follicle is a dry fruit that opens along one seam to release its seeds. Unlike a capsule (which splits along multiple lines) or a legume (which splits along two sides), a follicle opens along just one side.
Structure
Key Features
- Single carpel origin: Develops from one simple pistil
- One-sided opening: Splits along ventral (belly) suture only
- Multiple seeds: Usually contains several to many seeds
- Dry at maturity: Not fleshy like drupes or berries
Common Examples
Temperate Plants:
- Milkweed (Asclepias)
- Larkspur, columbine (Ranunculaceae family)
- Magnolia (when aggregate, multiple follicles per flower)
Tropical Examples:
- Magnolia species
- Sterculia species (Panama tree)
Costa Rican Tree Follicles
Magnolia (Magnolia poasana)
The endangered Costa Rican magnolia produces an aggregate fruit of multiple follicles arranged spirally. Each follicle opens to reveal bright red seeds.
Panamá (Sterculia apetala)
Produces large woody follicles 10-15 cm long that split open like a boat, revealing black seeds with edible arils. The opened pods persist on the tree.
Seed Dispersal
Follicles have evolved various dispersal mechanisms:
- Wind: Light seeds with papery wings or silky hairs (milkweed)
- Gravity: Heavy seeds simply fall when pod opens
- Animals: Bright seed coats (red, orange) attract birds
Why It Matters
Understanding follicles helps with:
- Seed collection: Know when pods will open naturally
- Propagation: Timing seed harvest before dispersal
- Identification: Follicles are diagnostic for certain families
- Evolution: Shows relationship between plant families