A classification for excent ferns
Recent phylogenetic studies have revealed a basal dichotomy hithin plants, separating the lycophytes from theeuphyllophytes. Living euphyllophytes, in turn comprise two major clades:
The spermatophytes, which are in excess of 260,000 species and the monillophytes whit about 9,000 species, includinghorsetails, whisk ferns , and all euspoangite and leptosporangiate ferns, and all eusporangiate and leptosporanguate ferns . plants that are included in the pycophyte and fern clades are allspore-bearing or “seed-free” , and because of this common feature their members have been lumped together historically under various terms, such as #pteridophytes” and “ferns and fern allies” –paraphyleticassemblages of plants . the focus of this reclassification is exclusively on ferns characterized by lateral root origin in the endodermis , usually mesarch protoxylem in shoots a pseudoendospore,plasmodial tapetum and sperm cells with 30-1000 flagellae
Increasingly robust pylogenetic hypotheses for ferns utilizing data from morphology, seven choloplast markers , one numlear gene and, threemitochondrial genes prompt us to reevaluate the classification of these vascular plants. Multiple-gene phylogenetic analyses studies by Wolf , Wolf and al. Pryer & Schneider & al, Wikstrom&pryer, and Schuattplez & al, have griven rise to growing conviction in both the composition and relationships of taxa at familial and ordinal ranks. Five recent mnorphological analyses ofrelationships, by Pryer al, Schneider, Stevenson & Loconte, and Sneider & al. have increased support for the molecularbased consensus topology. For eusporangiate and basal leptosporangiate ferns,evidence is now sufficient to allow us to circumscribe confidently most clades and assign ranks . However. For some more derived leprosporangiate ferns the phyologeneti evidence is still...