92 The Irish Naturalist. February, 



and torn, and littered with guano ; and quantities of the lead- 

 ing plants, especially Sea Campion (Silene maritima), go to 

 line the innumerable nests that are scattered about. This 

 vegetation is composed of a limited number of species, but 

 varies in density and in the relative abundance of the plants 

 composing it. Silene maritima is often dominant ; sometimes 

 Sea-pink (Armeria maritima) takes its place (Plate 24), or 

 Scentless Feverfew {Matricaria inodora), or species of Atriplex. 

 On the north side of Lanibay Head Scurvy-grass {Cochlearia 

 officinalis) is absolutely dominant during the spring months, 

 clothing considerable areas with a snowy sheet of blossom, and 

 forming one of the most striking sights on the island ; but 

 during the summer, before the seedling plants attain a con- 

 siderable size, Matricaria inodora makes a brave display on 

 the Cochlearia ground. In other spots the sward takes the 

 form of a dense sheet of Spergularia rupestris, with Atriplex, 

 &c, as subdominant forms. The Yellow Stonecrop (Sedum 

 acre) also has here its headquarters ; and Henbane {Hyoscyamus 

 niger), Curled Dock (Rumex aispus), Hemlock {Conium 

 maculatum), Cow-Parsnip {Heracleitm Sphondylium) form 

 colonies. At the great Puffin villages, under Flint Rock, the 

 trampling and digging operations are so severe as almost to 

 exterminate vegetation, and result in certain places in bare 

 slopes of crumbling brown earth. 



1 he Grass Associations. 



The grass areas still correspond closely with the limits of 

 the old farm-land, as shown by the remains offences, and by 

 the older editions of the Ordnance maps. It is difficult here 

 to distinguish between cause and effect, and to decide in how 

 far the old fences may have been erected along the limits of 

 natural grass formations, or how far they show the extent to 

 which other associations have been cleared off the land. It is 

 probable that the lower grass-land in the west is a natural 

 formation, and that it is in a state of equilibrium, and will 

 remain so as long as the present abundance of graminivorous 

 animals is there to check the Brambles, or Bracken, that might 

 otherwise invade it. The upland grass is, more probably, a 

 relic of husbandry, and will, in part at least, eventually be 

 destroyed by the Bracken and Heath associations which 



