1914-15.] BOTANICAL SOCIETY OF EDINBURGH 361 



the appearance of instability. Sooner or later the sand 

 gets blown away and the lower haulms and the roots 

 become exposed in the little " sand cliffs/' 



Along the northern shore of the Culbins is a ridge 

 which has the Marram grass well distributed, and the 

 landward slope of the same dune shows this plant, alone 

 on the shifting sand of the summit, losing its dominance 

 as the conditions change towards the foot to fixed dune, 

 and at some points to dune-marsh. 



2. Fixed Dunes. 



Sand Sedge Association. — The commonest plant in the 

 hollows — which may be floored with gravel scattered in 

 fixed sand, with pure tixed sand, or with fixed sand in a 

 thin covering over peaty soil. — which lie right among the 

 high barren shifting dunes, is Carer wr&natruL. In these 

 parts of the Culbins it generally occurs alone, and its 

 typical mode of growth is very clearly seen — the long rows, 

 often bifurcating, crossing and intercrossing, of the shoots 

 which rise in succession along the underground creeping 

 rhizomes. This sedge also plays a dominant part on the 

 spaces of low elevation where shifting dune merges into 

 fixed dune, and on sand which has not yet quite lost its 

 mobility, and on sand which has reacquired it. It is also 

 locally dominant on the borders of the " open " fixed dune 

 and that more " closed '" with vegetation. 



Juncus squwrrosus is another locally dominant member 

 of the fixed dune flora, and the other representative plants 

 are similar to those most generally characteristic of the 

 fixed dune flora in the Findhorn Bay Margin area. 



On the extreme east of the Culbin Sandhills, just to the 

 west of the Binsness pine wood, much denudation has 

 taken place, as evidenced by the exposed roots of Co.Uuna 

 and rhizomes of Garex arenaria. Low ridges of sand are 

 being piled up just within the border of the wood. At 

 some parts near here, however, the surface of the low 

 dunes is being covered again with sand. Partial binding 

 is supplied by low mounds of Calluna vulgaris, by Salix 

 repens. by Cladonia rangiferina, and Cladonia coecifera, 

 (Linn.\ Willd. The Salix re^ens is here much attacked by 



TRAN*. BOT. SOC. EDL>\ VOL. XXVI. 26 



