82 COLONSAY 



certain species preponderating to a greater degree in certain 

 situations than in others, every hill-side presenting consider- 

 able variety in species, and more so in the frequency with 

 which the species occur. 



There is reason to believe that grassy pastures, during the 

 last half-century, have decreased in area and deteriorated in 

 quality as regards the composition of the herbage. What 

 within living memory was greensward has now in many 

 places a permanent covering of heather, or is, in summer, 

 .adorned with fronds of the ubiquitous bracken. The 

 heather is slowly but surely spreading over the lower 

 hillocks and slopes. Much of the most porous and best- 

 drained land, through which its thick rhizomes can easily 

 penetrate, is overrun by the bracken. The aesthetic value 

 to the landscape of its summer green and its autumn tints 

 is more than outweighed by its debilitating effect on the 

 attenuated herbage underneath. 



The herbage in the majority of the pastures, whether well 

 drained or not, has a foundation, often dense, of moss an 

 undesirable product of a too moist climate. A few fields on 

 the boulder clay have been noticed where this form of 

 vegetation is only present in comparatively small quantities. 

 Animals cannot help grazing it along with the other herbage, 

 but it is avowedly bad for them and difficult to digest. 

 Hypnum squarrosum, Hypnum splendens, Barbula ruralis, 

 .are among the common species. 



Influence of Sheep on Pastures. Although it has not been 

 directly proved that sheep have actually exterminated a single 

 species of plant, there is evidence to show that they have to 

 a certain extent upset the balance of nature, and aided in the 

 preponderance of certain kinds over others, the coarsest and 

 least valuable over the finest and most nutritious. With 

 their narrow noses and sharp teeth, sheep nibble the finer 

 grasses and herbage close to the ground, and in the perpetual 

 struggle for supremacy that is silently but constantly going 



