"Apical dominance" in the sporangiophore of the fungus Phycomyces.

Control, by the spores, over the elongation and the branching of the sporangiophore is described. If the sporangium is removed from a sporangiophore, the sporangiophore stops growing within a few hours. 6-16h later a branch grows from the defunct growing zone. This branch forms a new sporangium and spores, and then starts to elongate again. The original growing zone can be "rescued" by replacing the sporangium with another sporangium or a sporangium-sized drop of spores. If the original growing zone is rescued, then it continues growing and the sporangiophore does not form a branch. It can only be rescued, however, within the first 60 min after the original sporangium is removed.