Brenchley . — The Weeds of Arable Land. ILL 147 
dominant. (This species is said to be particularly common among fruit 
trees in plantations.) 
Poa trivialis. Found on loam and clay. Never dominant. 
Equisetaceae. Equisetum arvense . Associated with most types of soil, 
but less common on sand and absent from chalk. Occasionally dominant. 
The classification of the weeds with regard to the soils they colonize is 
more difficult when dealing with the drift soils than when the directly 
derived soils are concerned. Well-marked soils as clay, chalk, and sand are 
relatively scarce, while loams of all categories are in the ascendant. 
Generally speaking, the soils are more intermediate in type than in any 
of the districts investigated previously. Still, an analysis of the lists shows 
that the weeds do fall into well-defined classes, loam taking its place for the 
first time as a special subdivision. 
A. Clay and Heavy Loam. 
Fields in this section were comparatively seldom seen, only about 
11 per cent, of the total number being really heavy in nature. The heavy 
soils were chiefly located round Harleston and Bressingham, where they are 
derived from the Boulder Clay (so being of drift origin), and again in the 
neighbourhood of Snettisham and Marham. At Snettisham the heavy clay 
land is down near the sea and is apparently also derived from Boulder 
Clay, but at Marham an outcrop of the Gault occurs, exceedingly heavy clay 
being met with cheek by jowl with the sharply defined Chalk outcrop. The 
dividing line between the two formations is remarkably distinct in this district. 
As is so usually the case, while plenty of varieties of weeds occur 
on clay soils as well as in other habitats, only a few species have a decided 
preference for the heavy lands, and practically none can be designated 
as absolutely symptomatic of clay, though a few are certainly characteristic. 
The following were found in association with these soils : 
Alopecurus myosuroides 
Geranium dissectum 
Heracleum Sphondylium 
Linaria Elatine 
Potentilla reptans 
Ranunculus arvensis 
Stachys palustris 
Equisetum arvense 
Euphorbia exigua 
Galium Aparine 
Tussilago Farfara 
Matricaria Chamomilla — only seen on heavy loam and sand. 
Never on clay. 
- characteristic. 
relatively frequent on these soils, 
but found on other types as 
well. 
