PRIMULA ELATIOR IN BRITAIN. 189 
approach to an elevated plateau as the Eastern Counties can boast. 
It will be observed, in the second place, that the Area covers 
only the upper portions of the valleys of the rivers which run 
out of it. The valleys of the Stort, Chelmer, Pant, Brett, 
Kennett, and Bourne all, as they leave the Oxlip-Area, produce 
more or less slight indentations in its margin; those of the 
Colne, the Stour, and the Lark produce remarkably sharp and 
deep indentations ; while that of the Cam actually cuts the Area 
into two portions—the Eastern and Western Districts already 
mentioned. The latter is the only river that runs actually 
through the Oxlip-Area. These river-valleys are, evidently, to a 
large extent responsible for the extreme sinuosity of the outline 
of the Oxlip-Area. Ifthe boundaries of the Oxlip-Area be laid 
down on an Ordnance Map, a third fact becomes apparent— 
namely, that those boundaries scarcely anywhere descend below 
the 200-feet contour-line, thereby, of course, avoiding all but the 
upper portions of the river-valleys, as already mentioned. The 
bulk of the Oxlip-Area appears to lie at an elevation of from 200 
to 400 feet, with a mean elevation of about 300 feet, the highest 
point within it (that about Saffron Walden and West Wratting) 
Teaching the higher figure in several places. It can hardly be 
“upposed that so small an elevation as 200 feet can alone 
"uence in any way the distribution of Primula elatior or any 
men plant. Probably, therefore, there exists some co-related 
act which governs the distribution of Primula elatior; and this 
appears to be the case. 
"s boundaries of the Oxlip-Area be laid down with care 
will b * Drift maps (Ordnance) of the Geological Survey, it 
Boulde seen that the Oxlip is most rigidly confined to the 
Gault ak nowhere extending off it on to the Chalk, the 
any of the Mi ensand, the River and Glacial Gravels, or on to 
aldere er formations and deposits which abut upon é ° 
clay area "d area, except where these extend into the Bou p 
eXtreine] Very narrow strips or occur within it in patehes o 
approrinat i extent. Nevertheless, the Oxlip does not even 
area of East, occupy the whole of the extensive Boulder-clay 
Oxlip-Area ern England ; nor even does the boundary of the 
area, except sa where coincide with that of the Boulder-clay 
line of both ong the north-western border, where the boundary- 
or) coincides almost exactly with that of the Chalk. 
P2 
