The inner Integument — Its probable origin and homology

Typological and ecological considerations point to the homology of the outer integument of the bitegmic chlamydospermous and angiospermous ovules with the single integument of the “lower” cycadophytic Gymnosperms. The inner integument either originated de novo or developed out of an accessory organ of the ovule (for which the membranous extension of the macrosporangial = nucellar wall already forming the primary pollen chamber in pteridospermous presemina comes to mind). Arguments are adduced in favour of the second alternative, but either interpretation implies that the outer and the inner integuments are inhomologous.