Jan. 1901.] BOTANICAL SOCIETY OF EDINBURGH 29 



of soil, with insufficient nourishment for trees to become of 

 any size and to bear much fruit. Among herbaceous plants, 

 an arrested distribution of a rare native species due to these 

 animals has come under my observation in the case of 

 Mertensia maritima. In one locality this species occurs on 

 a small island in an arm of the sea, but not on the adjoining 

 mainland. In 1891, one plant made its appearance on the 

 sandy shore of the mainland close to this island. It had 

 found a favourable site, and the plants increased in number 

 for a year or two, and would doubtless have continued to 

 spread but were discovered by rabbits, which destroyed them. 

 As an instance of a prevented spread of an introduced weed, 

 I may give Lcpidmrn Smithii. This species appeared among 

 sown grass in 1887, and increased by seeding until 1890, 

 when it was found out by rabbits and exterminated. As 

 these animals now occur in great abundance in many places, 

 similar cases must be frequent, though perhaps not often 

 noticed. 



Other changes in the ilora since the eighteenth century 

 may be mentioned, such as those caused by draining, 

 increased roadmaking, and more recently by railways. 

 Drainage, except as preparatory to reclamation of land for 

 cultivation, which has already been spoken of, has probably 

 had little effect on the flora of the West Highlands, as, from 

 the nature of the ground and of the kind of soil, only small 

 portions of any locality can be drained. The native vegeta- 

 tion remains unaltered by the larger part surrounding being 

 incapable of permanent improvement, and, except in ground 

 kept under rotation of crops, returns in a few years to its 

 former condition. The effect of making roads is to increase 

 the distriVjution of certain species which are already in the 

 district ; railways, on the other hand, bring new species. 

 The most common communication between districts in the 

 eighteenth century was by footpaths only. These have 

 little effect in increasing the distribution of species. If the 

 paths be through a peaty country, the only plants which 

 increase along them appear to be Juncus hiifonius and Carex 

 ovalis. If the path be in a loamy or gravelly country, we 

 find Plantago major spreading along it. The next stage, 

 and the most common means of communication at the 

 present time, is the bridle path or rough cart track. Here, 



