ON THE PLANT REMAINS OF THE SCOTTISH PEAT MOSSES. 795 



THE AREAS INVESTIGATED. 



1. Shetland. 



(One-inch Ordnance Survey, sheets 125, 126, 127, 128, and 130).— In 1909 a 

 second visit was made to Shetland for the purpose of settling some questions 

 suggested by an examination of the material obtained from the Walls district in 1906. 

 In addition to this, it was desirable to investigate some of the large areas of peat else- 

 where in these islands. In many parts of Shetland, and particularly in the Walls and 

 Northmaven districts, large areas of peat have been cut for fuel, resulting in the 

 exposure of numerous long sections which in most cases go down to the glacial drift. 

 These sections are nearly always situated either upon steep slopes or undulating 

 ground. 



During the last visit to this area a large number of sections and borings were taken 

 over the untouched moorland, and a comparison of these sections with those exposed 

 by the peat-cutters shows very clearly that the deposits began their growth at two 

 distinct times. These two growths can be distinguished from one another by their 

 stratification and position. 



The stratification of the older deposits can be summarised as follows : — 



1. Peat formed of Scirpus, Eriophorum, Sphagnum, and Calluna, not stratified. 



2. A bed about 3-6 inches in thickness containing arctic plants. 



3. Peat formed of Sphagnum and Eriophorum. 



4. A forest bed of Betula verrucosa, Ehrh., Gorylus avellana, and temperate wood- 



land marsh plants. 



5. Arctic plants. 



6. Glacial drift. In the mud between the stones immediately under the peat occur 



the remains of a fresh- water plankton : Navicula viridis, Kutz., Cosmarium 

 Meneghinii, Breb., Epithemia Argus (Ehrenb.), Kutz., amongst other forms. 

 These characteristic beds may locally be separated by thin beds of Phragmites 

 or Eriophorum. The average total thickness of this peat is from 12 feet to 

 17 feet. 

 The newer deposits exhibit no stratification, and consist throughout of the remains 

 of Calluna, Scirpus, Eriophorum, and Sphagnum. Small patches may occur at different 

 levels composed entirely of Sphagnum or Eriophorum, as shown in Plate III. fig. 5, 

 the lighter streaks being Sphagnum, but no true stratification can be made out 

 in the sections as a whole. The basal layers of peat in this series and the upper 

 layers of drift upon which they rest merit detailed description. No arctic vegetation 

 can be distinguished at the base of this peat. The lowest 2 or 3 inches is much com- 

 pressed, and contains numerous small flakes and fragments of birch bark, small birch 

 twigs, stone cells similar to those present in the cortex of birch stems, and xylem 

 elements. The peat is underlaid by 12 inches of closely packed stones, with fine sand 

 and loam between. Here and there occur patches where the finer material is mixed 



