Abstract
During the development of Agaricus bisporus morphogenetic cell death occurs. Histological sections reveal an early stage in which a loose and well demarcated area of tissue shows a cribriform pattern as a result of cell death. This process precedes the basidial differentiation and produces a hymenial split. The selective site, the precise timing, and the explicit occurrence prior to the basidial differentiation, suggest that the occurrence of morphogenetic cell death is genetically programmed in Agaricus bisporus. The function of cell death in developing primordia together with its peculiar morphology, to some extent, make this phenomenon comparable to cell death in apoptosis taking place in animal tissues.