Modified stems.
- Rhizomes (iris) are horizontal stems that grow just below the surface,
and can produce shoots from axillary buds along the stem.
- Bulbs (onion) are underground shoots that store food in layers of modified leaves.
- Stolons (strawberry) are horizontal stems ("runners") that grow along the surface.
New shoots can form at axillary buds along each runner.
- Tubers (potatoes) are enlarged rhizomes specialized for storing food.
The "eyes" on a potato are axillary buds that can form new shoots.