Descriptor : Pores of vertical intervallar structures
Descriptor type : categorical
Vertical intervallar structures: Longitudinal and often radial structures inside the intervallum (septa, taeniae...). 
Intervallum: Space enclosed between the walls.
- Aporous
 
- 
Aporous: No pore.
 
- Circular pores
 
- 
 
- Tetragonal pores
 
- 
 
- isn't included in the term
 
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