19^3- Praeokr. — Phancrooamia of Sallccs. i8 
been greatly altered since Mr. Hart made his list, and 
furnishes a very interesting study. 
Some of the leading types of the vegetation, as it now 
exists, may be briefly described. To take first the area 
which was never under cultivation, but much of which was 
grazed. At the Puffin colonies at the S. and S.W. margins 
of the island, a pure sward of Spcrgularia rupcstris occupies 
conspicuous areas. Above this, at both ends of the island, 
where rocky ridges and knolls stand up and innumerable 
gulls breed, Silcnc mayitima, often quite unmixed with 
other species, forms the vegetation, presenting at the time 
of our visit a most characteristic colour and appearance, 
visible from a long distance. Where the soil is deeper, 
great sheets of Rumex Acetosa and R. Acetosella, exceedingly 
luxuriant, are often dominant, plentifully mixed in places 
with Holcus mollis and Scilla nutans. Where the bird 
population is thinner, Pteris Aquilina becomes dominant, 
growing very tall and dense, and sheltering vast quantities 
of Scilla nutans, which forms a continuous undergrowth 
over many acres. All over the island, in both the unfilled 
and formerly tilled areas, one is struck by the bold grouping 
of the plants, associations covering wide areas being formed 
almost exclusively of two or three or four species. Some 
of these present rather unexpected groupings. Among the 
best -marked associations of the Pteris formation are : — 
1. Pteris Aquilina + Scilla nutans. 
2. Pteris Aquilina + Scilla nutans + Rumex Acetosa 
+ Nepeta Glechoma (a common type). 
3. Pteris Aquilina + Hydrocotyle vulgaris + Scilla 
nutans. 
To turn to the area formerly cultivated ; this presents 
a great contrast to the rank vegetation of the rest of the 
island. The old fences, and the clay slope that fring^ 
the long straight N.W. coast of the island, are indeed 
occupied by a luxuriant coarse vegetation — thistles, docks, 
nettles, and Ragwort. But elsewhere the vegetation 
invading the old cultivation is often as close as if a lawn- 
A 2 
