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INTERGLACIAL DEPOSITS IN SUFFOLK
the area after the retreat of the ice. Some species of plants may be present only in a particular interglacial period. This kind of evidence may make it possible to identify a given deposit as belonging to one particular interglacial, and consequently the deposits above and below it may be referred to known major glaciations. The work on the interglacial deposits of Suffolk is not sufficiently far advanced to make possible any conclusions about the number of interglacials and glaciations. Several interglacial deposits containing pollen are known in the county. At least two of them, at Hoxne and Saint Cross South Elmham, lie in hollows in a blue chalky boulder clay. Both of these deposits are being studied at the moment, and the pollen spectra from them suggest that they belong to the same interglacial period. The deposit covering the interglacial at Hoxne has for many years been a source of controversy; Reid Moir regarded it as a partially decalcified chalky boulder clay, but it may, in part, be a solifluction deposit. Thus it is not known for certain whether an ice sheet extended over the area after the Hoxne interglacial, but there is evidence that periglacial conditions were present at some period subsequent to the interglacial. The evidence at Hoxne, then, shows a sequence of glaciation—interglacial—glacial or periglacial. It is not possible at the moment to make any correlation of these deposits with those of other parts of Britain and the Continent. Further studies along these lines on other Suffolk interglacials may provide more evidence about the succession of events during the Great Ice Age and their correlation.
A NOTE ON FOSSIL WATER-FERNS IN
SUFFOLK
T w o genera of water-ferns, Azolla and Salvinia, have been recently discovered in interglacial deposits in Suffolk. Both these genera are new to the British Pleistocene Flora, but have been found in interglacial deposits on the Continent. Azolla was found in the deposits at the classic site of Hoxne, and Salvinia in the interglacial deposit recently discovered by Mr. Spencer at Bobbitt's Hole, near Ipswich. Only the male and female spores of the plants have been found so far. The spores of the fossil Azolla are very similar to those of the modern A. filiculoides, Lam., a species which was introduced into Britain towards the end of the nineteenth Century. The species of fossil Salvinia has not yet been determined. The botanical and geological significance of these interglacial fossils is being studied in detail. R. G.
WEST.