Rhynie chert, drawing
Fig.2: Cut face of Rhynie chert with numerous sections of Horneophyton
sporangia, with or without spores (Sections
of other parts have been omitted). Note the pipe-like lobe (far left), the big
bag with two small columella cross-sections
(centre), and the thick base of the branching columella (far right). Two columella
cross-sections seen in a two-lobed
section (far left) indicate that the sporangium had four lobes at least.