lx FLORA ORCADENSIS. 
long, but a detailed study of the relation of such 
groups of plants has not been made till quite recently. 
We find groups of quite dissimilar plants forming 
communities according to the nature of the soil. 
There are heathy, marshy, and sea-shore communities, 
as well as those of sand-dunes and _ salt-marshes. 
Take as an example the sand-dunes. Most of the 
plants are binders: Psamma arenaria, Carex aren- 
aria, Triticum jgunceum, and Triticum repens. 
There is a large area of land in Orkney which has 
not yet been cultivated, so that there is ample room 
for associations of plants. In many little lochs plant 
communities are gradually filling them up, and ulti- 
mately swampy meadow-land will have been formed. 
No better illustration of this can be seen than the 
platforms of bullrush and Phalaris arundacea formed 
in some lochs. These plants with stiff stems catch 
the drift of the lochs—weeds and broken reeds— 
until several lochs have spaces like huge platforms 
formed out into the water, often in a crescent shape, 
at the edge of which bullrushes and stiff grasses push 
out, farther and farther, year by year, until there is 
left this fertile land which bears the local name of 
the “reeds.” These recovered areas can be seen in 
most of our smaller lochs, as in Isbister, Banks, and 
Sabiston Lochs, Birsay ; Greemeshall Loch, Holm ; 
Bea, Sanday; Milldam, Westray ; and Wasdale, Firth 
A few years ago, a strong easterly gale, with high tide, 
laid bare several yards of soil beneath a sand-bank in 
Newark Bay. A whole net-work of interwoven roots 
of sand-binders, closely matted, showed how perfectly 
these perform the task of sand-binding. 
