Jan. 1901.] BOTANICAL SOCIETY OF EDINBURGH 23 



The local manner in which agricultural weeds are distributed 

 in the Highlands is interesting. Land around some town- 

 ships may have abundance of weeds, such as Viola arvensis 

 or Euphorhia Helioscopia, and they may not be again met 

 with for some miles, the intervening farms or crofter 

 holdings being without them. This points to probable 

 separate centres of introduction, and to the species not 

 being able to spread along the intermediate uncultivated 

 ground. Some species can spread from one village to 

 another along roadsides, as is the case with Taraxacum 

 officinale and Cardamine hirsuta ; but if those centres are 

 only connected by roads through peaty soil without gravel, 

 this extension does not take place. Some effect on the 

 quantity of weeds on cultivated ground must have taken 

 place when a change of manure was introduced in such 

 fields. In the eighteenth century farmers had no byres, 

 consequently no dunghills were formed, and seaware, with 

 occasionally brackens, was the only manure used, and sea- 

 ware is free from weeds. 



A comparison of the flora of existing cultivated ground 

 with that of ground formerly under crops, or on disused 

 crofts, gives some insight into the question of what species 

 are undoubted natives, capable of holding their own with 

 the remainder of the vegetation. When former cultivated 

 areas on exposed sites are examined, we find the flora now 

 to be in no way different from that of the surrounding 

 uncultivated ground, except that there are often more 

 brackens, due to the soil being better than in the sur- 

 rounding parts. In the shelter of the house walls will 

 frequently be found Urtica dioica, Arctium minus, and 

 Gnicus lanceolatus, a stray plant of the latter occasionally 

 finding its way to the immediate neighbourhood. These 

 plants do not take a firm hold of the ground except where 

 man, cattle, or sheep frequent. Nettles are occasionally 

 seen some distance up the hill, but always in cattle or 

 sheep shelters, natural or artificial. Where the crofts have 

 been in sheltered ground, a few more weeds have been able 

 to retain their hold, but as they are most common in such 

 places, or in ground at present under cultivation,they cannot be 

 considered as being of the same standing as the undoubtedly 

 long-established native flora. Among these may be mentioned 



