The Articulated and Non-Articulated Stem in Selaginella (Selaginellaceae - Lycopodiopsida)

The present investigation presents a clear differentiation between the articulated and non-articulated stem of Selaginella, based on morphological and anatomical characteristics. We also take the first step in developing a clear definition of the articulated stem in Selaginella. Further, in Selaginella anaclasta previously described as having articulate stems, we found no micro-morphological or structural evidence of articulations, and we describe this species as one with non-articulated stems. In support of our findings, we present micromorphological and structural descriptions of three species S. anaclasta, S. exaltata, and S. parviarticulata, which differentiate the various stem constructions in Selaginella.