Abstract
The present paper deals with the chemistry and ultrastructure of the cell wall of Tasmanites punctatus Newton, Tasmanites erraticus Eisenack and undetermined species of Leiosphaeridia Eisenack. Infra-red microspectrometry has revealed absorption bands interpreted as being due to the presence of COOH, CH2 and CH3 groups. Ultrastructural differences are shown between T. punctatus, T. erraticus and Leiosphaeridia.