244 The Scottish Naturalist. 



progressed, it seemed to me advisable to modify this first design r 

 and to include all the casuals of this district of which I could find 

 a record. It will be readily understood that "The Botanist's 

 Guide " of my teacher and predecessor, Dr. Dickie, has been my 

 chief source of information, apart from personal investigations. 

 In several cases I have found myself constrained to differ from 

 him in the conclusions to which I have come in respect to the 

 claims of certain plants to be regarded as indigenous in the north- 

 east of Scotland ; hence some of those admitted by him seem to 

 me to be open to dispute as natives, while others placed by him 

 among introduced species might fairly claim a place in our native 

 flora. It must, however, be constantly borne in mind that such 

 questions are, by the nature of the case, very hard to decide 

 beyond dispute. There is good reason to believe that no smalL 

 proportion of species admitted without controversy or mark of 

 doubt into British Floras, were originally introduced by man, 

 though unintentionally so. I refer to the numerous weeds of culti- 

 vated ground, such as the poppies, some spurges, speedwells, and 

 others that it would be tedious to specify. There are certain, 

 others that can hardly be called weeds of cultivation, but that are 

 seldom, if ever, to be seen at a distance from human habitations,, 

 and that delight to grow on ruins or on ground rich in nitrogenous 

 substances — e.g., on dung-stances. Among such may be instanced 

 the nettles, the common goosefoot, &c. If left to struggle for 

 existence with other plants, unaided by the interference of man- 

 kind, these species are apt to be crushed out of the situations for- 

 merly occupied by them, and thereby prove their inability to have 

 in the first instance spread as unaided colonists into the places, 

 where we now see them. Again, we find that plants show very 

 different powers of establishing themselves in a new locality, when 

 by any chance they are brought into it. Some species are so well 

 fitted to survive in the struggle that in a few years they oust the 

 original occupants to a great extent, and themselves spread so 

 widely, and become so abundant, that they would readily be re- 

 garded as native, were we not able, through fortunate circumstances, 

 to trace their past histories. 



Of such plants in our own neighbourhood, Mimulus hitens, Ver- 

 onica Buxbaiunii, Aigopodium podagraria, Lupinus perennis, and 

 Elodca canadensis, are examples. Some grasses have a wide distri- 

 bution given them from being employed in the mixtures used by 



