Or many protoxylems. When the protoxylem strands are situated at the periphery of the stele, abutting on the pericycle, as in all roots, and many of the more primitive Pteridophyte stems, the stele is said to be exarch.
When the protoxylems have an intermediate position the stele is inesarch (many Pteridophytes and some of the more primitive Phanerogams).
The protoxylems and the phloem strands are developed alternately, just within the outer limit of the young cylinder.
The anatomy of Lycopodium presents considerable variety in detail, but the stem is always monostelic and the development of the xylem centripetal, the protoxylems being situated at the periphery of the stele; pericycle and endodermis surround the stele, and the wide cortex may be more or less sclerenchymatous.