(For further details on the form and arrangement of the flower and its parts, see Flower.) Each stamen generally bears four pollen-sacs (microsporangia) which are associated to form the anther, and carried up on a stalk or filament.
The development of the microsporangia and the contained spores (pollen -grains) P (P g is closely comparable with that of the microsporangia in Gymnosperms or heterosporous ferns.
A typical male flower consists of a central axis bearing numerous spirally-arranged sporophylls (stamens), each of which consists of a slender stalk (filament) terminating distally in a more or less prominent knob or triangular scale, and bearing two or more pollen-sacs (microsporangia) on its lower surface.
They consist either of microsporangia or megasporangia, which are arranged in basipetal succession on the receptacle.
Each sorus includes both microsporangia, with numerous spores, and megasporangia, each of which contains a single megaspore with a complicated wall.