stem, and elongated sporangia, taller than wide, borne at the ends of fertile branch systems which are differentiated from other branches. Like some Psilophyton species, Aarabia had short side branches in which the last sections curved back on themselves. On the other hand, Aarabia had relatively few sporangia in each fertile branching unit and they were single, not paired, whereas most trimerophytes had large clusters of sporangia carried in pairs which were often twisted around one another.

Meyer-Berthaud