The Division Lycopodiophyta (sometimes called Lycophyta) is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant (living) vascular plant division at around 420 million years old, and includes some of the most "primitive" extant species. These species reproduce by shedding spores and have macroscopic alternation of generations, although some are homosporous while others are heterosporous. They differ from all other vascular plants in having microphylls, leaves that have only a single vascular trace (vein) rather than the much more complex megaphylls found in ferns and seed plants.
There are around 1,200 living species divided into three main groups within the Lycopodiophyta, sometimes separated at the level of order and sometimes at the level of class. These are subdivided at the class level here:
Class Lycopodiopsida – clubmosses and firmosses
Class Selaginellopsida – spikemosses
Class Isoetopsida – quillworts and scale trees
The members of this division have a long evolutionary history, and fossils are abundant worldwide, especially in coal deposits. In fact, most known genera are extinct. The Silurian species Baragwanathia longifolia represents the earliest identifable Lycopodiophyta, while some Cooksonia seem to be related.
From Wikipedia, the free encyclopedia