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a division of extinct higher plants the remains of which have been traced to the Silurian and Lower and Middle Devonian periods. The Psilophyta had dichotomously branching stems. Leaves and roots were absent, and sporangia were borne on the ends of the shoots. The stem had a thin central cylinder (stele) with protoxylem in the center, and it was covered with a stomatous epidermis. The plants were marked by homospory. The Psilophyta are regarded as the primitive group that gave rise to higher cormophytic plants.