LINNEAN SOCIETY OF LONDOIf. 87 



Salix berbacea, Linn. 



Isolepis setacea, li. Ilr. 



Eleocbai'is palustris, It. Br. 

 Carex dioica, Liun. 



echinata, Murr. 



jjauicea, Linn, 



flava, Linn. 



Holcus lanalus, Unit, 

 Dactylus glomcrata, Liun. 

 Poa trivialis, Linn. 

 *Pinus sylvestris, Linn. 



*Quercus Robur, Linn. 

 *Corylus Avellana, Linn. 

 *Betiila alba, I^inn. 

 ¥rWn\\B glutinosa, Linn. 

 :tPotamogetoa lieteroplijllus, Schirb. 



pusillugi, Linn. 



* pectinatiis, fjinn. 



■xZinnichellia paliisiris, Linn. 

 *Sparganiuiii raniosuni. Muds. 

 *Scirpiis lacustris, Linn. 



Three other species are found in these beds whicli indicate a 

 colder temperature : — 



Empeti'um nigrum, Ljinn. 

 Salix herbacea, Liiin. 

 ■ifTsoetes lacustris, Linn. 



A very large proportion of the plants now enumerated from 

 the Interglaeial beds are either aquatic or water-loving plants. 

 Ten of them are woody plants. The Mora, as a whole, represents 

 the general type of the existing English Plor.i. It is not a little 

 remarkable to tind these plants growing on the ground cleared of 

 ice during a warm interval in the glacial period. This interval 

 must have lasted sufficiently long to permit the return of the 

 plants, and their establishment in these localities. 



Another decrease in the temperature caused the advance of 

 the land-ice, and the re-destruction of the vegetation. The 

 newer Boulder Clay is the evidence of this fresh advance, and as 

 the terminal debris of the retreating ice-cap it is also the 

 evidence of the final disappearance of the great Ice Age. The 

 improving temperature once more brought back the ancient 

 vegetation. We find its remains in the sedimentary deposits 

 above the Boulder Clays, and in the older peats. The two sub- 

 arctic species, Betula nana, Linn., and Isoefes lacustris, Linn., 

 occur in these later glacial deposits in England, though in our 

 existing vegetation they have retired to the North or to the moun- 

 tains. Seven species are found in the later glacial beds which 

 are now scattered over England and the South of Scotland. 

 These are : — 



Nuphar liitcuiu, Sm. 

 ffinantlie Lachenalii, C. Gmel. 

 Sambucus nigra, Linn. 

 Ceratopliyllum demersum, Linn. 

 Salix repens, Linn. 

 Potauiogeton crispum, Linn. 

 Taxus baccata, Linn. 



Twenty-four species are now scattered over the whole of 



Britain, namely : — 



Ranunculus sceleratus, Ijinn. 



Flammula, Linn. 



repens, Linn. 



Lychnis Flos-Cuculi, Linn. 

 Prunus Padus, Linn. 



Rubus Idffius, Linn. 

 Eu})atoriuiu cannabinuni, Linn. 

 Taraxacum oflicinalc, Wigc/ov. 

 Menyanthes trifolinta, Linn. 

 r>artsia Odontites, Linn. 



* Species found also in the ]jo\ver Glacial deposit at Cromer. 



