Certain species of fungi of the genus Aspergillus produce a type of cells around the cleistothecium that are called hülle cells. To facilitate the analysis of the formation of these cells, an Aspergillus nidulans strain with high hülle cell production was obtained. Hülle cells from this strain were allowed to grow on dialysis membranes, where it was possible to observe their nuclei. The material was fixed with Carnoy, hydrolyzed with HCl and stained with Giemsa. Several nuclei approximately equal in size to the nuclei of hyphae and conidia were observed during the phase of hülle cell formation. The formation of a macronucleus measuring approximately 3.1 mum was observed in mature hülle cells. To compare the DNA amount, hülle cells and conidia of the CH-89 strain were isolated and submitted to DNA extraction (Tuyl, 1977). The amount of DNA per cell was, on average, 17.2 times greater than the amount of DNA in the conidia.