148 TRANSACTIONS OF THE [Sess, LXxv. 
Sub-formation [V.—Maritime pasture. 
Sub-formations III. and IV. are excluded as belonging 
to other formations. ; 
Possibly calcareous pasture on limestone and chalk might 
form a swb-formation ITT. in other areas, but there is none 
such in Orkney, and [ have not studied it anywhere. 
ForRMATION IL—WET PASTURE. 
Owing to ground water from whatever cause, the sub- 
soil is not dry even in summer. No determinations of 
water content were made, so I am not yet able to com- 
pare in this respect the wettest ground that I include as 
wet pasture with that of a marsh, but apparently in some 
cases the soil may be as wet as in the latter, but is less 
stagnant and probably richer in food salts. Of course the 
line of separation is purely arbitrary. The distinction 
that I usually employed lay in the vegetation, viz. the 
dominance of the grasses. In a few cases perhaps where 
they are not dominant the abundance of Trifoliwm repens 
suggests meadow rather than marsh. 
As regards the division into sub-formations tabulated 
above, it can scarcely be said that the distinction “acid” 
and “neutral” is rigid in my grouping of the associations 
in I. and IL. 
Soils too wet as well as too acid for true meadow are 
included in the “ Marsh-Meadow and Wet Pasture” division. 
The distinction in the character of the vegetation is the 
presence im I. of a large percentage of marsh plants or 
sometimes plants of wet heath. 
It was found that in Orkney true neutral meadow could 
be recognised occupying only very limited areas. 
Nor was there any very characteristic association on 
these areas that could not be referred either to marsh- 
meadow or to neutral pasture (dry). I have therefore 
decided to omit any special description of neutral meadow, 
on the basis of the limited material afforded for its study 
in Orkney. 
As a consequence some of the types described under sub- 
formation I, such as the Aira ccspitosa association, 
ought perhaps to be referred to sub-formation II. 
