The developmental types within the family Agaricaceae vary considerably but it looks as if the ontogenetic pattern is not without regularity. About 20 species have been examined. On one side the stipitocarpous genera Cystoderma, Phaeolepiota, and Chamaemyces, on the other side genera with highly concentrated primordia like Macrolepiota and Agaricus (isocarpous, pileocarpous or hymenocarpous). Lepiota, Leucocoprinus and Leucoagaricus with a more concentrated development may occupy an intermediate position. Some remarks are made on developmental problems in Squamanita. In Chamaemyces fracidus the radiating elements on the cap are not a palisadodermium sensu stricto but they belong to the universal veil. However this structure is limited to the pileus-surface, so we have to suppose that an ontogenetic factor affects in some way the formation of the pileus and that of these radiating elements. In other species a layer of tightly packed, erect elements forming part of the universal veil envelops also the pileus-margin and the upper part of the stem (with Lepiota clypeolaria at the outside and with Lepiota ignipes as an emanating veil at the inside of the universal veil). A trichodermium which is afterwards changed into a paradermium is to be found in Leucocoprinus whereas a true palisadodermium occurs in Macrolepiota.