The Cyanophyceae are one of the lowest orders of plants, lying between the Bacteria on the one hand and the Chlorophyceae or green algae, on the other. They occur in salt or fresh water and are often a cause of the pollution of water supplies. They frequently form slimy masses upon rocks, trees, or soil if a sufficient supply of moisture makes growth possible. They often form symbiotic relations with fungi thus constituting lichens, an interesting and widely spread group of organisms. In connection with the roots of some higher plants they sometimes form nodules due to the stimulation and hypertrophy of their hosts. The range of colour is as great as that of habitat. [...]

Macallum, A. (Supervisors)

Lloyd, F. (Supervisors)