ioo Brenchley.— The Weeds of Arable Land in 
2 . Fuller’s earth ; an argillaceous deposit between I and 3. Below 
the surface this appears as a very sticky yellow clay. 
3. Bath or Great Oolite ; clay and limestone. 
In the Wilmington district, on the further side of the valley from the 
above, the soil is derived from — 
1. Lower Lias ; clay and limestone. 
2 . Inferior Oolite. 
[In both these districts there is an outcrop of the Midford Sands, but 
this is generally either wooded or under pasture, and so does not affect the 
investigation in hand,] 
The derivation of the soils does not appear to affect the varieties of 
plants occurring, as the different species of clay weeds were found indis- 
criminately on land derived from all the four geological formations, all 
being calcareous in nature. 
The number of species occurring was relatively less than those found 
on chalky soils, and the majority of the plants were such as occurred on 
any type of soil, hardly one appearing to be symptomatic of clay. A very 
few species, however, were chiefly associated with clay, though occurring 
on other types of soil as well, and one, Plantago media , appears to be 
confined to clay in this district. 
Plantago media— practically confined to clay. 
Capsella Bursa-pastoris — also recorded from loam. 
Mentha arvensis \ 
Poa annua chiefly found on clay, but also 
Ranunculus arvensis ( seen on other soils. 
Tussilago Farfara 
Ranunculus acris — also on sand. 
Brassica alba 
Euphorbia exigua 
Plantago major 
Polygonum aviculare 
„ Convolvulus 
Potentilla anserina 
B. Chalk. 
also on chalk. 
The chalk districts investigated were chiefly on the Wiltshire Downs 
in the neighbourhood of Shrewton and Stonehenge, a radius of some four 
miles being worked. Data were also obtained from the chalk at Heytesbury 
and Sutton Veny, not far from Warminster. The whole of the soils were 
derived from the chalk formation, though for convenience of working and 
classification they were subdivided into — 
