Practice question

Cooksonia and related genera Rhynia, Aglaophyton from mid Silurian to Early Devonian represent earliest unequivocal vascular plants assigned to extinct phylum Rhyniophyta, now considered basal polysporangiophytes or protracheophytes. They possessed dichotomously branching naked axes with terminal sporangia and simple S-type annular tracheids, but lacked true roots and leaves. Bryophyta are nonvascular, while Lycophyta and Monilophyta diversified later from zosterophyll ancestors. Rhyniophytes document critical transition from bryophyte-grade poikilohydry to true vascular homoiohydry during initial terrestrialization. This structural framework illustrates phylogenetic relationships and adaptive significance highlighted in competitive examinations focusing on comparative plant morphology and systematics.