FINAL REMARKS 473 



have come thus as new members of the fauna, they at 

 least add their numbers to the somewhat scanty native 

 stock, to the great damage of young pines throughout the 

 land. 



Fig. 85. Some Chance Introductions to Great Britain ; shown diagrammatically, 

 associated with the country of their origin. 



FINAL REMARKS 



The increase and extension of commerce is an end to- 

 wards which all civilized nations have worked, yet a reading 

 of the summaries given in this chapter will show that 

 the gain in these respects has been no unmixed blessing. 

 "Half the weeds of American agriculture/' Professor Riley 

 once said, "and a large proportion of her worst insect pests, 

 have been imported among us from Europe"; and Europe's 

 debt to America stands little in arrears we think of the 

 Canadian water weed (Anacharis canadensis], the tangled 



