The thallus of the lichen Ramalina menziesii (Tayl.) is comprised of subunits which resemble planar nets. The nets arise upon older nets as buds which develop perforations and expand. Microphotographic study of thallus development in the field shows several features which differ from a recently proposed model of development for this species. New perforations develop continually in new tissue produced at the apical margin of the net. The apical margin is inrolled, and may furcate. This type of branching is developmentally distinct from the formation of new nets from buds borne upon expanded parts of the net. Anatomical study of net apices appears to support assertions that programmed tissue necrosis contributes to perforation formation at sites where gaps are present in the algar layer.