megasporangiate strobilus development stage megasporangiate strobilus open stage In some species, seed cones reclose and open multiple times before seeds dehisce. For those species, the seed cones are in this stage after the first time they open, even if they re-close, although it may be hard to know. A megasporangiate strobilus (seed cone) development stage, beginning when the scales of a seed cone have opened for pollination and ending when the seeds have fully dehisced. For seed cones that do not dehisce, this stage ends when seed cones have dropped from the plant.