Spontaneous epigenetic transition between two silencing states. The percentage of cop1-like endogene silenced plants is given for seedling and adult stages of the T2 and T3 generations of (A) type C loci, (B) type L loci, and (C) type E loci. Note: Adult plants had been preselected on kanamycin. Thus, homozygosity dependent silencing (typical for type L adults, see horizontal line) gives 33% silenced plants. Seedlings were scored independent of kanamycin selection. Hence, homozygosity dependent silencing (typical for type E seedlings) gives 25% silenced plants.