THE ONTOGENY OF PYCNIDIA OF GUIGNARDIA-BIDWELLII IN CULTURE

The ontogeny of pycnidia in Guignardia bidwellii was studied under in vitro conditions. The first developmental stage consists of a paraplec tenchymatous primordial nodule embedded in a stroma. It develops into a fertile centre (stage 2) from which originate radiating conidiogenou s filaments covering the pycnidial cavity (stage 3). At the fourth sta ge hyaline conidia are produced and ostiole formation takes place at t he top of the cavity, in the pycnidial neck. Comparisons are made with the pycnidia of other Sphaeropsidales and some Ascolichens.