TOPOGRAPHICAL BOTANY OF SCOTLAND 175 



for or against afforded by other localities. Of the existence 

 of such errors, of commission as well as of omission, careful 

 revision has made me only too fully aware, and I very much 

 regret their occurrence, and have felt that they ought to be 

 pointed out and corrected. But since 1900 much fresh 

 information has been gained and made known regarding the 

 distribution of the flora of Scotland in this journal, in the 

 "Journal of Botany," and in the publications of various 

 Societies. I have also to thank several friends for letters 

 containing valuable notes, and personal observations have 

 added considerably to my knowledge of the plants of north- 

 eastern Scotland. 



As the following pages will show, these additions and 

 corrections affect by far the greater number of the species 

 already mentioned, and they will also include mention of a 

 large number of additional species detected in Scotland 

 within recent years, even though all but a few of these addi- 

 tions must be regarded as mere " casuals," unable to retain 

 their place for more than a brief time. So long as they are 

 clearly recognised and indicated as casuals, it is well to note 

 their presence, even if but to note the fact that they have 

 failed to acquire a footing when brought into the country in 

 some way. Many species now well established in Scotland 

 (e.g. Mimulus Langsdoi-ffii, now so abundant in ditches and 

 by streams) must have passed through the " casual " stage in, 

 perhaps, a not very remote past ; and it is desirable to record 

 when they were first observed, and how they gained their 

 place against adverse conditions. 



For convenience of reference the names have been re- 

 tained as given in the former paper, except where evidently 

 erroneous determinations. 



The term alien is used to denote a plant that owes its 

 presence in Scotland to human agency, whether intentionally 

 introduced for use or ornament, or unintentionally, as weeds 

 mixed with cultivated plants, or by the operations of industry 

 or commerce. Aliens include (i) plants of cultivation, most 

 of which die out soon, unless intentionally protected and 

 favoured by man ; (2) colonists, or weeds of ground under 

 regular cultivation, which die out when such cultivation 

 ceases, though difficult to extirpate while it is continued ; 



