'72 A XEW FLOEA OF 



expected. The greatest concentration of these boreal plants is, 

 we see, in the most southern of the districts. The special rich- 

 ness of Teesdale in Montane species is a fact which we cannot 

 undertake to explain ; but if the relative abundance with which 

 these plants occur in the different districts were to be taken into 

 consideration, the contrast would be much more striking than it 

 is now. The small proportion of the total number of species 

 which any other district, except that of the Tees, yields is note- 

 worthy, especially the lowness of the figure for district number 

 one, which, besides being the most northern in position, contains 

 the high Cheviot peaks, and a wide area of elevated ground. 

 "We may take the even distribution of a considerable number of 

 these plants through the districts as indicating (what is a cha- 

 racteristic feature of the physical geography of the two counties) 

 the large extent of surface which is occupied by low hilly coun- 

 try, a circumstance which explains also a point upon which we 

 shall afterwards have occasion to dwell, and the large number of 

 plants common in the south and centre of England that come to 

 a stop in their wanderings towards the north within our bounds. 

 So much premised by way of introduction, we will now take the 

 districts seriatim. 



1. TWEED AND TILL DISTEICT. 



The Tweed altogether drains an area of 1870 square miles, 

 including nearly the whole of Eoxburghshire, Berwickshire, 

 Peeblesshire, and Selkirkshire, and portions of Haddingtonshire, 

 Edinburghshire, Lanarkshire, and Northumberland. At the 

 town of Peebles, 50 miles from the coast in a direct line, it is 

 only 500 feet above sea-level in altitude. For about 18 miles 

 in a direct line the main branch forms the northern boundary of 

 Northumberland, a broad sinuous stream, flowing more rapidly 

 than is usual with rivers of so large a size, past Carham, Corn- 

 hill, Tillmouth, Twizell, and the ruined castle of Norhamto 

 Eerwick. The banks are in some places level and grassy, but 

 sometimes steep and wooded. The influence of the tide reaches 

 up to Norham, which is 1 miles inland. There is a small burn 



