IW spines projecting radially across orifice to form screen

knowledge base : exist
structure : inner wall
Stipules : Present on inner carcass wall
Carcass perforations: inner wall (IW) : isn't included in the term
Carcass external plates: inner carcass wall (IW) : isn't included in the term
Type of morphological tubes (IW) : isn't included in the term
Additional sheath : Present on inner wall
Type of additional sheath (IW) : Sieve formed by protrusions
Repartition of bracts on secondary sheath (IW) : isn't included in the term
Type of sieve (IW) : Radial protrusions forming screen
Repartition of micropores (IW) : Regular