82 OUR ROCK-GARDEN 



United States recognised one hundred and thirty- 

 seven plants as introductions from foreign countries, 

 principally from England, but this number has now 

 more than doubled. Chickweed was introduced by 

 a bird-fancier : in ten years it had spread in all 

 directions over fifty miles from the little hamlet 

 in South Carolina where it started, and is now 

 hopelessly irremovable. 1 It is rather striking, too, 

 that these British plants often attain to a greater 

 vigour in congenial foreign countries than at home, 

 the imported thistles in Australia and America 

 thriving with an excess of vigour that the un- 

 sympathetic landowner bitterly regrets. A New 

 Zealand correspondent tells that he has seen 

 thistledown lying in some places a foot in depth 

 on newly cleared forest land, while the watercress 

 and brooklime seriously threaten to divert the 

 courses of the rivers. Furze, broom, sweetbriar, 

 blackberry, all plants that we can here keep well 

 under control, are in the Southern Hemisphere very 

 expensive to keep down. Shepherd's purse, hore- 

 hound, willow herb, ox-eye daisy, mouse-ear, chick- 

 weed, and numerous other plants are all settling 

 down, while the English wild flowers, such as the 



1 A friend near Sydney asked us to send him some 

 dandelion seed, as he had had the plant so highly com- 

 mended medicinally, but we declined the responsibility of 

 starting millions of dandelion seed-heads blowing over 

 Australia. 



