Volume 82, 1954-55
– 209 –

Acknowledgments
I am chiefly indebted to Mr. R. A. Hicks, of the Auckland Metropolitan Drainage Board, with whose co-operation this work was carried out. Dr. Pringsheim kindly studied samples which were sent to Cambridge. The work was carried out at Victoria University College during the tenure of a Research
– 210 –

Scholarship, and is partly included in a thesis submitted for the degree of Doctor of Philosophy.
