-psədə noun plural
Usage: capitalized
Etymology: New Latin, from sphen- + -opsis + -ida
: a subdivison of Tracheophyta comprising vascular plants (as the horsetails and extinct related forms) with jointed stems, small leaves usually in whorls at distinct stem nodes, and sporangia in sporangiophores and including the orders Hyeniales, Sphenophyllales, and Equisetales — compare lycopsida , psilopsida , pteropsida