Biological studies on the rivulariaceae

Abstract

This thesis reports a study on the variation of two genera of blue-green algae, Calothrix and Rivularla. The aspects chosen for detailed study were tapering and the hair. Before any comparative work could be undertaken it was necessary to develop ways of describing, in a quantitative manner, changes in the tapering and hair length. Tapering proved to be complex to describe in a satisfactory manner but four simple indices have been suggested. Measurements of individual trichomes have shown problems inherent in detailed studies of tapering, and the indices suggested by the author have been discussed in relation to this. Experimental studies on tapering have been concerned with elaborating the observations of previous authors that, in the presence of combined nitrogen, Calothrix and Gloeotrichia did not develop their characteristic taper. The effect of combined nitrogen on morphology was studied using the tapering indices. Attempts to culture material with hairs proved difficult; however a few factors which affect the development of the hair have been described. A computer program was developed in order to summarise relationships between the occurrence of hairs and other morphological features which have been described in the literature. For practical reasons it was often necessary to assign a name to members of the genus Rivularia; however in doing this many problems were encountered. To overcome some of these difficulties an objective method of identification was devised. This was used in particular to identify material collected in the field. A brief ecological survey of Rivularia was undertaken in order to study possible correlations between certain aspects of water chemistry and the occurrence of members of the genus.