160 Brenckley.— The Weeds of Arable Land in relation to 
Of these Bartsia Odontites and Mentha arvensis may be regarded as 
practically confined to clay, while Polygonum Convolvidus finds its home 
on clay or sandy soils only. 
Bo Chalk. 
This includes both the chalk proper and the heavy chalk marl under- 
lying it. The flora on these soils is somewhat sharply marked out, in that 
several plants which are otherwise universal in distribution are totally absent, 
because they are calcifuges. 
Bromus sp. 
Geranium pusillum 
Scabiosa arvensis 
Sherardia arvensis 
Silene Cucubalus 
Brassica alba 
Fumaria officinalis 
Geranium molle 
Agrostis stolonifera 
Alchemilla arvensis 
Brassica Sinapis 
Lychnis vespertina 
Poa trivialis 
Viola tricolor 
C. Light and Sandy Loam, including Sand. 
These soils are of very mixed origin, as all the light lands on the differ- 
ent geological formations (excluding chalk) fall under this heading. Thus 
the loams may either be derived from — 
(1) Alluvium, 
(2) Lower Greensand ; 
or they may be loams originating from drift overlying — 
(1) Gault, 
(2) Oxford Clay ; 
while the sands proper are either — 
(1) Alluvial sands, or 
(2) Lower Greensand. 
However, it is evident that the derivation of the soil has little or no 
effect upon the distribution of the weeds, the texture being the determining 
feature. 
Chrysanthemum segetum } are confined to sand and are very sympto- 
Rumex Acetosella r matic, being probably associated 
Spergula arvensis ) with acid soil conditions. 
► are symptomatic of chalk. 
, 
} while very characteristic of chalk are 
also frequently found on sandy 
soils. 
\ 
> are of very frequent occurrence. 
