ECOLOGY OF WOODLAND PLANTS. 363 
Distribution of the Plants of the Millstone-Grit and 
Coal-Measure Areas, as affected by Soils. 
It is evident from the above observations that a change of 
geological formations and soil-conditions is accompanied by a 
change of plant formations. 
In illustration of this we will take the upper central portion 
of the district shown on the maps figs. 9 & 10 (pp. 352-3), that is, 
the part covered by sheet 260 of the 6-inch Ordnance-Survey 
map. Herethe two well-marked biological types occur, xerophytes 
and mesophytes, and their distribution has been worked out on 
the6-inch map, special attention being paid to the transition region 
from the Millstone-Grits to the Coal-Measures. On the map 
fig. 11 (p. 364) the results are shown reduced to the 1-inch scale. 
Fig. 12 shows the geology of the same area, the details being 
taken from sheet 260 of the 6-inch Geological-Survey map, and, 
as in fig. 11, reduced to the 1-inch scale. Glacial deposits are 
entirely absent, and, except for the formations of peat already 
referred to, the soils owe their origin mainly to the denudation 
of the underlying rocks, and therefore a comparison may, I think, 
be fairly made with the solid geology map. 
If we now make a comparison of the two maps figs. 11 & 12, 
we find them both instructive and suggestive. Pteris, as we 
have seen, is abundant in both areas, but its associates differ 
considerably as we pass from one formation to the other. The 
xerophytes are seen to follow pretty closely the Millstone-Grit 
and Coal-Measure sandstones, except in the exposed, elevated 
regions; while the mesophytes indicate as clearly the shales 
and clays. 
To render comparison easy, the same signs are used on the two 
maps: the blaekened areas indicate shales aud clays on the 
geological map and Mesophytes on the vegetation map; the other 
sign indieates respectively sandstones and Xerophytes, a small 
semi-xerophytie area is indieated by dotting. 
Considerable differences occur in the physiological water in 
soils over beds indicated by the general term shales, and a more 
detailed study of these is in progress on lines similar to those 
followed by Hedgecock (45). 
In some instances, Xerophytes are absent over areas indicated 
as sandstone on the Geological Map, as in Woodsome and 
