The Origin of our British Flora 



and S. arbuscula), of the dwarf birch, Arctostaphylos, 

 Empetrum, and the blaeberries (Vaccinium myrtillus 

 and V. uHginosa),"^ and may have resembled the usual 

 arctic tundra (see p. 92). But there are several sub- 

 arctic plants which ought to be added to this list, but 

 which would not occur in those peat bogs from which 

 evidence on these questions is usually obtained. Thus 

 scurvy grass, Armeria, and Plantago maritima are both 

 arctic plants, seashore plants, and also occur as alpines 

 or sub-alpines in Scotland. It has sometimes been found 

 difficult to understand why they should grow both along 

 the sea and on rocky ledges at over 2000 feet. But 

 the occupation of the land began on the seashore and 

 gradually extended to the hills, so that the mountain 

 scurvy grasses probably flourished at some time or other 

 in all the intervening regions where they have been now 

 choked out by other species. 



Besides these, several estuarine and marsh plants, 

 including some of the most important land-formers, can 

 also endure an arctic climate. There are, e.g., Scirpus 

 Tabernaemontani and S. lacustris, Phragmites, the two 

 Triglochins, Menyanthes, Litorella, and others which 

 seem to range into the subarctic, if not always to the 

 true arctic regions. 



So that even in the Dryas time there may have been 

 quite a considerable occupation and colonisation of the 

 river valleys and estuarine mud. 



For the next or birch time, perhaps the North Cape 

 of Norway or the Lofoden Islands might be the best 

 example. It was still a very cold Britain with a July 

 temperature of only 9° C, and in August 7° to 8° C. 

 Along with the birch were alder, hazel, and probably 

 dwarf juniper. On the Continent Populus tremulus, the 

 aspen poplar, seems to have been characteristic. With 



* Lewis. 

 222 



