In protostele xylem surrounds phloem. The type includes Haplostele, Actinostele, Plectostele and mixed protostele.
1. Haplostele: Xylem surrounded by phloem is known as haplostele.
2. Actinostele: Star shaped xylem core is surrounded by phloem is known as actinostele.
E.g. Lycopodium serratum.
3. Plectostele: Xylem plates alternates with phloem plates.
E.g. Lycopodium clavatum.
4. Mixed prototostele: Xylem groups uniformly scattered in the phloem.
E.g. Lycopodium cernuum.