14 INTRODUCTION. 



very late introduction, and several species of Ouscuta 

 have been undeniably imported with seeds from 

 abroad in the present day. Mr. JAMES MOTLEY dis- 

 covered Malva verticillata in company with _M". crispa 

 in corn-fields near Llanelly, Glamorgan shire, a few 

 years ago, both perhaps escapes from gardens ; and 

 Dr. BKOMFIELD has recorded, in the Pliytologist, how 

 Melampyrum arvense was introduced into the Isle of 

 Wight with seed corn from the eastern counties. All 

 arable ground, manured soil, or abandoned gardens, 

 must then be viewed with distrust, and the plants 

 upon them considered at best as only in a naturalized 

 state, or introductions of cultivation. European plants 

 are thus now carried by voyagers into the western 

 regions of the world, as of old continental plants 

 migrated to Britain. Indeed, as WILLDENOW observes, 

 " the wars in which different nations have been en- 

 gaged, their migrations, and crusades, the travels of 

 different merchants, and commerce itself, have brought 

 a number of plants to us, and transplanted ours to 

 foreign countries. Almost all our culinary plants 

 came from Italy or the East, as well as most species 

 of corn." * 



* The rotation of cultivation that any piece of land undergoes, must 

 undoubtedly greatly affect the plants spontaneously growing upon it, 

 which, in the event of a change of crop, will be unable to maintain their 

 position, and for a period they may altogether disappear, whilst new 

 weeds will creep in with the fresh seed. On the other hand, a fallow 

 piece will invite the immigration of a host of intruders, who can, how- 

 ever, scarcely have time to mature their projects, and fly off, before the 

 plough dislodges them. It sometimes happens that flowers exist in a 

 field, which being annually mown for hay, they have not time either to 

 produce their blossoms, or mature their seeds, before the crop is carried 

 off. In this case they may remain in obscurity for many years, until 

 the pasture being left for grazing, they then rise up to flower, and seed 

 profusely, in the hussocky spots, which cattle are sure to leave at intervals, 

 and surprise the eye by their unexpected appearance. But when an 



