BRITAIN. 



251 



Gaut (1904) has described the zonal vegetation of a lowland pasture, and 

 marsh, derived probably from the silting up of a stream: 



The lowermost portion was a reed swamp, followed first by a zone of 

 Ranunculus repens, and then one of R. acris. The portion beyond was char- 

 acterized by Cynosurus cristatus, and this was followed by a zone of Des- 

 champsia caespitosa, Alopecurus pratensis and Holcus lanatus. 



Moss (1904) has studied the peat-moors of the Pennines with especial 

 reference to their age and origin, and concludes that they originated in morasses 

 formed probably by the destruction of primitive woods, which were not only 

 more extensive, but also reached a higher level than the present relicts, and 

 that the peat-moors are later than the Britons, but earher than the Saxons, and 

 proba,bly date from the Roman conquest, i. e., they are not older than 2000 

 years. 



W. G. and R. Smith (1905) defined associations due to man or cattle as 

 "substituted" (secondary formations of Warming), of which farmland and 

 tree plantations are the typical examples in Scotland. An account is given 

 of the sand-dime vegetation under two types: (a) dry sandy ridges with mari- 

 time grasses, and (b) moist dune hollows with plants of salt mud, or grasses 

 and sedges. The shifting of population from loose to fixed dunes is shown by 

 lists. 



Sprague (1906) has studied the growth of a small shingle island in a stream 

 rising in mountains, and has made a comparative study of invasion from the 

 various adjacent habitats, reaching the conclusion that a very large percentage 

 of the species had come from near-by associations. 



Moss (1907) has summed up the course of succession on moors, dunes, and 

 on limestone in Somerset by means of the diagrams shown in figiu-e 12: 

 Moor Sere 



Aquafic vegetation of BJrch and pine 



peaty hollows left by plaatations 



ttirf cutters 



N 



Callaria heath 



Myrrca, Tetrallx and MoGnia heatlis 



t 



Primitive aquatic vegetation 



Limestone Sere 



Ash wood 

 Limestone cliffs T 



I J^Ash copse 



Limestone screes I 



Limestone heath 



t 



Farmland of ttie 

 peat moors 



Dune Sere 

 Sandy maritime farmland 



t t 



Dune ponds and marshes Dune pasture 



Sward-forming associations (Carex, Festuca) 



- \ .1 



^ \ Association of Ammophila arundinacea 



Derelict pastors I ^~~~~^~~~ 



Farmland Association of Agropyrum junceum 



FiQ. 12. — Moor, limestone, and dime serea in Somerset, England. After Moss. 



