Pteridophytes exhibit diverse branching patterns. Dichotomous branching, where the apical meristem divides into two equal branches, is common in primitive forms like Psilotum. Monopodial branching, where a single main axis continues to grow and produces lateral branches, is also observed in more advanced pteridophytes. Both patterns represent different evolutionary strategies for maximizing light capture and structural stability in these plants.

Equisetum is the sole living genus of the class Sphenopsida (or Equisetopsida). Within this class, the genus is classified under the order Equisetales. This order is characterized by plants with jointed stems, whorled leaves, and strobili at the tips of fertile branches, representing a group that was much more diverse during the Carboniferous period.

Apospory is a type of apomixis where the gametophyte develops directly from the vegetative or somatic cells of the sporophyte, bypassing the normal meiotic process that produces spores. This results in a gametophyte that has the same ploidy level as the sporophyte.

Psilotum is traditionally classified within the class Psilopsida. This class represents one of the most primitive groups of vascular plants, characterized by a simple body structure consisting of a dichotomously branched stem. While modern molecular phylogenetics may refine these groupings, Psilopsida remains the standard taxonomic assignment in many botanical curricula for this specific genus.