82 III. INTRODUCED SPECIES. 



have trul}' native localities on rocks and banks about the 

 coast. — PetroseUnum sativum is cultivated in every gar- 

 den ; springing up profuselj'^ from self-sown seeds. It 

 has become established on the sea -cliffs in various 

 places ; and it is seen occasionally about the sites of for- 

 mer gardens inland. Some English botanists have in 

 consequence reported it native ; but the greater number 

 of them more correctly consent to regard it as an intro- 

 duced species, naturalised by escape from gardens. — Me- 

 lissa officinalis is alwaji-s allowed to be an alien, although 

 recorded as if now becoming established in some spots. — 

 Marrubium vulgare is seldom questioned ; yet many of its 

 localities are highly to be suspected. A few x^lants of it, 

 scattered about old farm houses and other country 

 abodes, often represent a recorded locality. — Atropa Bel- 

 ladonna is supposed to be native in some calcareous 

 tracts ; but many of its localities have a very suspicious 

 proximity to old abbeys and monasteries. 



6. Way -side plants, &c. — The greater number of sus- 

 pected species belong to the categories of corn-field weeds 

 and garden plants. Some few others of them are seldom 

 or never seen as weeds among field crops, are seldom 

 or never cultivated in gardens. If not native they may 

 have been accidentally introduced among ballast thrown 

 ashore from ships, or intermingled with merchandize of 

 various kinds. Examples are mentioned in the valuable 

 Flora of Hertfordshire, by the Rev. Messieurs Webb and 

 Coleman, of species probably introduced to that county 

 among seeds of flax and cole, brought to the Oil-mills. 

 The ballast deposited in the provinces of Tyne and Hum- 

 ber, by returned coal-vessels, has furnished species to 

 lengthen the list of nominally English plants in those 

 provinces. And botanic gardens have done some little in 

 this way, by introducing weed-like species which might 



