Advance in solution of the manifold problems of interpreting the distribution of the components of the British flora is apparently suspended until we may resoIve the old dilemma of the extent to which the species now in these islands survived the last Ice Age here (possibly in areas they now occupy), and, conversely, of the extent to which they have had to re-immigrate. Over this issue powerful arguments have been raised for and against per-glacial survival, but as may be judged from the report of the Royal Society discussion upon this topic in 1935, agreement has never been within sight. This paper is written in the belief that the evidence now being brought to light by studies of conditions in the Late-Glacial period, go a considerable way to resolve the problem, and, indeed, to show how the arguments of both schools may be reconciled. In large part the evidence consists of identifications of fruits, seeds and pollen grains from sites which, on grounds of stratigraphy, flora, and fauna are known with fair certainty to have formed in the Late-Glacial period or at the opening of the Post-Glacial period. These identifications, in part, are already published, and in part have been made in the subdepartment of Quaternary Research in Cambridge, and will be published fully in due course. I am much obliged to my colleagues and students for permission to mention in this general way some of the identifications they have made. A very brief summary in Science Progress (Godwin, 1947) draws attention to the substantial recent advance in our knowledge of Late-Glacial conditions in north-west Europe. The period is defined as that between the commencement of retreat of the ice from Denmark and northern Germany up to the beginning of retreat from the great central Swedish end-moraines. It has been shown that after this latter date, approximately 8500 B.C., woodland cover existed over southern Scandinavia, but before this the landscape was one of tree-less tundra, or of tundra broken by small copses of tree-birches, the 'Park-tundra' of Iversen. A temporary amelioration of climate, followed by a recession during the Late-Glacial period, has been widely recognized and is described as the Aller0d oscillation. During this warm phase more or less closed birchwoods were found in southern Denmark and pinewoods grew in Holstein. In the cold periods before and after the Aller0d warm stage 'cryoturbatic' phenomena are widely recognized; it is evident that solifluction was prevalent and that the open soil surface was much exposed to displacement by frost, water and wind, whilst big spreads of gravels, sands and loess afforded sites for temporary establishment of plants. Macroscopic remains from these periods show-abundant Dryas octopetala, Betula nana, Salix herbacea, 4rmeria vulgaris, Empetrum nigrum and plants of similar character, but it is from pollen analyses, now abundant, that one can reconstruct the general character of the vegetation. Pollen of herbaceous plants greatly outweighs that of trees (birch and pine), and a large part of it consists of grass and sedge pollen. In addition, the pollen grains of many herbaceous plants