PLANT DISTRIBUTION. 177 



appeared farther north at the entrance to Pascoe Farm, on the 

 hedge separating the trap-rock quarry from the high road. In 

 both cases the cause of the big jump in the wanderings of 

 Linaria is clearly traceable. The new hedge at Devas was built 

 of stone brought from Mabe, with which the seed of the 

 wanderers undoubtedly came, At Pascoe Farm, Linaria first 

 appeared on the inside of the hedge, and on watching the case I 

 found that near this very spot the carters always dropped their 

 rugs, nosebags, &c., after returning from Mabe and other places 

 whither they had taken stone for road metalling. In this 

 instance the seed must have been introduced by the rugs, &c. 

 At both places the plant has increased with marked rapidity. 



Mimulus luteus, the Monkey plant, and Elodea canadensis 

 the Canadian pond-weed (which Charles Kingsley newly named 

 the " Canadian curse"), are very recent additions. Both plants 

 are natives of North America ; but wherever they gain a footing 

 in Britain they become naturalised, and oftentimes they sweep 

 all native species before them. Mimulus has been creeping up 

 the valley alongside the river at the rate of one mile in five years. 

 Elodea has a very simple history. Four years ago, as an experi- 

 ment, I planted a sprig of about three inches in length in a pond 

 in the valley, little expecting it would grow; but it has Justly 

 warranted Charles Kingsley' s strong expression, in that from 

 this small piece two ponds are now filled. 



In the same year a Surrey botanist sent me a puny specimen 

 of Impatiens Parviflora a peculiar but somewhat graceful looking 

 Balsam, now tolerably common along the river banks in a few of 

 the eastern counties. This was planted in my garden. The next 

 summer a few plants appeared about 200 yards distant, and 

 during the past season two quarries near the viaduct were 

 crowded. 



Scrophularia Scorodonia, the Balm-leaved Fig-wort, one of 

 the rarest of British plants, has crept into the valley within the 

 past decade ; but, singularly enough, it keeps to one limited spot 

 near Perran wharf. 



Agrimonia Eupatoria, a valuable pot herb, is slowly 

 wandering west from the banks of the Truro river. From Feock 

 to St. Gluvias and Gwennap stray patches may be met. 



