The stele of Equisetum is of a very peculiar type whose relations are not completely clear.
The conjunctive of a root-stele possessing a pith is often sclerized between the pith and the pericycle.
Sometimes all the parenchyma within the stele undergoes this change.
In other cases, however, continuous primitive stele is developed, extending from the primar stem to the primary root, the leaf-traces arising later.
In cases where the development of the embryo is advanced at the resting period, traces run from the cotyledons and determine the symmetry of the stele of the primitive axis, the upperpart of which often shows stem-structure, in some respects at least, and is called the hypocoty- ledonary stem or hypocotyl, while the lower part is the primary root .~-,