1912-13.] BOTANICAL SOCIETY OF EDINBURGH 135 



erecta, Hampe ; Vaccinium Myrtillus, Linn.; birch seed- 

 lings ; Polytrichum commune, Linn. ; and other mosses. 



The plant associations of this disforested land evidently 

 come within the scope of the migratory formations of 

 Crampton (4), who mentions the " tendency on the part of 

 the plants of the more stable formations to eventually 

 obtain possession of areas formerly occupied by migratory 

 formations on the one hand, and of certain plants of the 

 migratory formations to invade disturbed areas of the stable 

 formation on the other." 



Tansley (5) points out that both in the plant formation 

 of clays and loams and the plant formation of sandy soil, 

 retrogressive associations are known — consequent upon 

 the clearing of woodland, and represented bj 7 scrub and 

 grassland. 



Clements (3) regards invasion as including both migra- 

 tion and ecesis, i.e. the adjustment of a plant to its habitat, 

 and defines the term as follows :— 



" By invasion is understood the movements of plants 

 from an area of a certain character into one of a different 

 character, and their colonisation in the latter." 



Warming (6) observes that when new soil arises anywhere 

 it is soon invaded by plants, and points out that new soil 

 may be produced by various agencies, man included. The 

 early vegetation of new soil is open, and many species are 

 found to belong to the local weed-flora. 



Regarding the future of this land one can only speculate. 

 It, however, appears probable that in the higher parts 

 grasses will eventually predominate and that a rough 

 meadow will result. On the other hand, the present 

 numbers of Rubus idaeus may increase and tend to mili- 

 tate against this by forming scrub or thicket. The pre- 

 dominance of Juncus effusus and the abundance of J. 

 articulatus and Descha/mpsia caespitosa would appear to 

 indicate that the lower lying and damper portions of the 

 present habitat are already being covered with a Ju ncetum 

 communis (of " Types "). 



The higher association of Juncus effusus containing 

 so many young birch trees, if left undisturbed, will un- 

 doubtedly pass into a natural birch wood, as has occurred 

 on the other side of the railway line. 



