216 COLIN CLOUT'S CALENDAR. 



European plants, must have come with the prevailing 

 winds and currents from some unknown land beyond the 

 sea. That the plants in question grew there even then 

 is highly probable, because most of them bear every sign 

 of great antiquity : certainly, they are not likely to have 

 been introduced by man, since the larger number are 

 mere inconspicuous water-plants, which could not come 

 over with cultivated seeds or tubers, and which would 

 not, of course, be deliberately planted in gardens. On 

 the other hand, when once introduced by chance, they 

 would be sure to gain a firm footing ; because America, 

 with its enormous stretches of fresh water, in rivers, 

 lakes, and innumerable scattered ponds, is far richer in 

 strong and well-endowed aquatic weeds than relatively 

 hilly and lakeless Europe. This peculiarity is well seen 

 in the career of the Canadian pondweed, which was first 

 introduced into England as a botanical specimen in 1847, 

 and rapidly spread through canals and sluggish waters 

 over the whole of Britain. No European weed can stand 

 against it ; and what makes its progress the more re- 

 markable is that it seldom or' never seeds in this coun- 

 try, propagating entirely by its lissom floating rootless 

 branches. Still, the area over which it has made its 

 way, and the centres from which it started Yorkshire, 

 Leicestershire, Berwick, and Edinburgh clearly show 

 (what is otherwise well known) that it owes its introduc- 

 tion to human means : while the spontaneous occurrence 

 of the other water-plants in a few lonely portions of the 

 western coasts equally suggests that they owe their trans- 

 plantation solely to birds or ocean-currents. 



