Abstract
The sporulation rhythm in Nectria cinnabarina Tode ex Fr. is expressed by either concentric rings or spirals. The period is inversely proportional to the temperature and does not approach 24 hours; the rhythm is therefore noncircadian. The period of the zonation rhythm is lengthened by culturing the fungus on a dialysis membrane over the agar surface, on media solidified with an increased amount of agar, or on media containing deuterium oxide. These observations suggest that the transfer of materials by diffusion between the colony and the substrate is a significant factor in regulating the period of the rhythm.