108 Brenchley . — The Weeds of Arable Land in 
6. Rhinanthus Crista-galli , Yellow Rattle, was very prevalent in some 
places in the West. Generally this is a weed of pasture land, but in one 
case observed the barley crop was full of it and was utterly ruined by it. 
Some seasons are far more favourable to the growth of this weed than 
others, though in both 1910 and 1911 large quantities have occurred in this 
particular district. 
7. The total absence of Mayweed, Matricaria inodora, was very 
noticeable. A small amount of Anthemis sp. occurred in places, but the 
plants rarely attained any size, and so a very conspicuous feature in the 
weed flora of Bedfordshire was missing in that of the West Country, on 
similar soils. 
8. Where two or more species of the same genus occur as weeds, it 
frequently happens that the species differ among themselves in their 
distribution, being associated with different types of soil ; e. g. — 
Euphorbia exigua 
chiefly on clay 
„ Helioscopia 
„ „ chalk 
Plantago lanceolata 
chalk only 
„ major 
chalk and clay 
„ media 
clay only 
Poa annua 
chiefly on clay 
„ pratensis 
chalk 
„ trivialis 
distributed 
Ranunculus acris 
clay and sand 
„ arvensis 
clay 
„ repens 
chiefly on chalk 
Rumex Acetosella 
acid sandy soil 
„ crispus 
chiefly on chalk 
Summary. 
X. In each district investigated a definite association exists between 
the species of weed plants and the soil on which they grow. This associa- 
tion may be either — 
(a) Local When a weed is symptomatic of a certain soil in one 
district but is not so exclusively associated with it in another. 
( b ) General. When a certain species is symptomatic or characteristic 
of the same type of soil in different districts. 
2. In most cases there is no association between the weed and the 
crop, though a few species do show a relationship. The weeds usually 
found in ‘ seed ’ crops appear to be constant, and certain other plants exhibit 
