What are Rays?
Rays are bands of cells that radiate outward from the center of a trunk like spokes of a wheel. They transport water and nutrients horizontally and store starch reserves. In finished lumber, rays create the attractive "flecks" or "figure" visible in quarter-sawn boards.
Structure
Types by Size
- Uniseriate rays: One cell wide — invisible to the naked eye.
- Multiseriate rays: Many cells wide — visible as prominent flecks (e.g., oak, roble).
- Aggregate rays: Groups of small rays appearing as one large ray.
Visual Appearance in Lumber
- Quarter-sawn surfaces: Rays appear as broad, shiny flecks (ray fleck or silver grain).
- Flat-sawn surfaces: Rays appear as fine lines on the end grain.
- End grain: Rays are visible as radial lines from pith to bark.
Costa Rican Examples
Roble Encino (Quercus spp.)
Large multiseriate rays produce the distinctive "silver grain" flecks characteristic of oak lumber worldwide.
Teca (Tectona grandis)
Fine rays contribute to the smooth, even texture that makes teak a premier furniture wood.
Practical Significance
- Figure and aesthetics: Prominent rays create prized decorative grain patterns.
- Splitting tendency: Wood splits more easily along rays; important for traditional shingle-making.
- Drying defects: Differential shrinkage along rays can cause checking.