Fungal endogenous rhythms expressed by spiral figures.

Culture zonations in two fungi, Nectria cinnabarina and Penicillium diversum, are expressions of endogenous rhythms. These culture zonations may take the form of either concentric rings or Archimedes' spirals. The rhythm in N. cinnabarina is noncircadian. The rhythm in P. diversum is relatively insensitive to temperature and has a period of approximately 24 hours. The lack of a demonstrable mechanism for phase shifting suggests that this rhythm may also be noncircadian.