WITH AND WITHOUT MANURE. 39 



cases the wheat is grown continuously year 

 after year. 



The plants which predominate in uncul- 

 tivated land depend both on the nature of the 

 soil and on the climate and situation. On poor 

 gravel, furze grows in abundance ; on peaty 

 uplands, short heath ; on cold, wet-bottomed 

 soils, rushes cover the ground. Natural woods 

 of birch and oak are found in sheltered High- 

 land glens, and self-sown Scotch firs spread 

 themselves in the neighbourhood of extensive 

 pine forests. 



