The affinity of Tmesipteris with the Sphenophyllales

The peculiar fertile structures of Tmesipteris and Psilotum have given rise to much discussion as to their morphological nature. The foliage leaves in Tmesipteris, as is well known, are simple, whereas the fertile structures are forked, that is, each has a stalk bearing leaf-like lobes, a bilocular sporangium or synangium being attached to the stalk just below the lobes. Three views have been taken as to the nature of these fertile structures— 1. The whole structure has been interpreted as a branch of the stem, being equivalent to a reduced Lycopodium spike. The lobes, according to this view, will be leaves. (Juraniyi, Strasburger, Sachs, Goebel.)