OF A CAMBRIDGESHIRE WOODLAND. 343 
soil is a bright yellow or brown colour and continues so with little alteration 
to considerable depths. This soil contains many more stones all through 
it than does the clay ; these are chiefly flints. Roots here also penetrate 
to a considerable depth, the shrubs’ roots extending to more than 25 inches. 
In the paper these two soils will be referred to as the calcareous clay or 
marl and the loam respectively. They are usually sharply marked off from 
one another with only a comparatively narrow band of intermediate soil. 
Some diggings were made on the clay side of this region. Here there 
were about 5 inches of fairly uniform soil coloured dark with humus. This 
soil is a mixture of clay and coarse sand ; up to about 18 inches the amount 
of sand is much less and the soil more yellowish in colour. Beyond about 
18 inches chalk begins to appear, and the soil below this is the same as the 
deeper layers of the calcareous clay. 
In general appearance these two soils are quite distinct ; in winter the 
calcareous clay becomes very wet and muddy, with water collecting in 
hollows, while in summer exposed parts become very dry and crack freely on 
the surface. The loam never gets so wet on the surface and does not crack 
and harden in dry weather to the sume extent. 
Some mechanical analyses of these soils have been undertaken. The two 
soils show certain distinct differences in the relative proportions of the fine 
and coarser grained materials. In the separation by subsidence the marl 
soils showed 30-40 per cent. of the very fine-grained materials or “ clay,” 
while the loam gave 20-25 per cent. The latter also showed a greater 
proportion of the sandy materials. The calcareous clay agrees fairly well 
with the soil from the London Clay mentioned by Hall *, as regards 
mechanical composition. Foreman t gives analyses of arable soils from the 
Cambridgeshire Boulder Clay which correspond with those in the wood :— 
Boulder Clay Boulder Clay 
over Gault, over Greensand. 
StONES E | 2-00 1-8 
Fine gravel ............ O38 067 
Coarse sand ............ 10°67 14:79 
l'ine VN 14:95 18:55 
ПОНИ 11:85 16°37 
MEDI NR 13°53 12°35 
"DEO ME 26:95 22:28 
Мопа{пге'.................. 2.66 3:24 
Loss оп ignition......... 9-6 773 
СаСОз occ. а cece ees 5.71 0:58 
In regard to chemical analysis, the chief point I have investigated is the 
percentage of lime, CaCO;. 
* Hall, 1908, p. 56. + Foreman, 1507, p. 168. 
LINN, JOURN.— BOTANY, VOL. XL. 25 
