798 



MR FRANCIS J. LEWIS 



unaltered boulder clay represents an old land-surface on which vegetation flourished 

 and died without forming peat, until at some period active peat formation began — 

 possibly due to a change of flora or of physical conditions — and resulted in the deposi- 

 tion of the 4 feet of peat which covers S4) much of the undulating moorland away from 

 the hills, and which has been so extensively dug for fuel. 



The changes produced in the flora at the present day due to the total removal of 

 large areas of peat are worthy of notice. In most cases the removal is by human 

 agency, the peat being cut in the spring, stacked, dried and carted during the 

 summer and autumn. In other cases, particularly near the west coast, fully exposed to 

 the wind, large areas of drift are being laid bare by natural agencies. 



The dominant plants on the newer peat series where the vegetation mat has not 







Fk;. 1. — Section in a quarry near Eela Water, Northniaven, Shetland, showing unstratified peat resting on drift. 



a, Peat ; b, 3 inches of granitic sand with humus and birch bark ; c, coarse granitic sand with clay, 



no humus ; d, iron- pan ; e, unaltered boulder clay. 



been broken are Calluna vulgaris forming a close sward, the plants being 3 to 8 inches 

 in height, Juncus squarrosus, Potentilla tormentilla, Eriophorum vaginatum, and 

 Erica Tetralix. When the whole of the peat is excavated, the stony layer of drift 

 resting on unaltered boulder clay is exposed. The earliest stage in the formation of a 

 new vegetation mat is represented by isolated plants of Festuca ovina, var. vivipara, 

 Plantago maritime/,, Galium saxatile, Juncus squarrosus, and a few plants of Nardus 

 stricta alternating with large stony areas devoid of vegetation. A later stage is repre- 

 sented when patches a few feet in diameter of Juncus squarrosus, Festuca ovina, var. 

 vivipara, and Nardus stricta are encountered. Very stunted prostrate plants of 

 Calluna and Potentilla tormentilla make their appearance amongst the tufts of Juncus 

 squarrosus and Nardus stricta, together with a few plants of Erica, cinerea and a small 

 amount of Rhacomitrium lanuginosum. In time these isolated tufts of vegetation 

 coalesce and a thin covering of vegetation is formed. The grasses maintain their 

 dominance, and the area which was formerly covered with 3 or 4 feet of peat maintains 



