He remarks that these plants, while including species now very widely scattered, present no appreciable change of characters.
Above this bed are glacial clays, which hold other species indicating an extremely cold climate. They are few in number, only _Salix polaris_, a thoroughly arctic species, and its ally, _S. cinerea_, L., and a moss, _Hypnum turgescens_, Schimp., no longer found in Britain, but an Alpine and arctic species. This bed belongs to the beginning of the Glacial period, the deposits of which have as yet afforded no plants in England. But plants occur in post-glacial and upper-glacial beds in different parts of England, to which Carruthers thus refers:
"The period of great cold, during which arctic ice extended far into temperate regions, was not favorable to vegetable life. But in some localities we have stratified clays with plant-remains later than the Glacial epoch, yet indicating that the great cold had not then entirely disappeared. In the lacustrine beds at Holderness is found a small birch (_Betula nana_, L.), now limited in Great Britain to some of the mountains of Scotland, but found in the arctic regions of the Old and New World and on Alpine districts in Europe, and with it _Prunus padus_, L., _Quercus robur_, L., _Corylus avellana_, L., _Alnus glutinosa_, L., and _Pinus sylvestris_, L. In the white clay-beds at Bovey Tracey of the same age there occur the leaves of _Arctostaphylos uva-ursi_, L., three species of willow, viz., _Salix cinerea_, L., _S. myrtilloides_, L., and _S. polaris_, Wahl., and in addition to our Alpine _Betula nana_, L., the more familiar _B. alba_, L. Two of these plants have been lost to our flora from the change of climate that has taken place, viz., _Salix myrtilloides_, L., and _S. polaris_, Wahl.; and _Betula nana_, L., has retreated to the mountains of Scotland. Three others (_Dryas octopetala_, L., _Arctostaphylos uva-ursi_, L., and _Salix herbacea_, L.) have withdrawn to the mountains of northern England, Wales, and Scotland, while the remainder are still found scattered over the country. Notwithstanding the diverse physical conditions to which these plants have been subjected, the remains preserved in these beds present no characters by which they can be distinguished from the living representatives of the species."