Botany - Anatomy of Flowering Plants Question with Solution | TestHub

Protostele is the simplest and considered to be the most primitive type of stele. It consists of a solid core of xylem surrounded by the cylinder of phloem, enclosing no pith. All other types of steles have evolved from it in the course of evolutionary specialization. Protosteles may be found in Selaginella, Lycopodium, Gleichenia and Lygodium among present day forms.