1 74 Stapledon . — On the Plant Communities of Farm Land. 
A few species are, as Brenchley has observed, practically confined 
to cereals ; on the Cotswolds this is true of 
Lap sana communis. Poa trivialis. 
Plantago media* 
* Becomes very abundant on leys that have been down for some years. 
In Mid-Wales this distinction does not hold, but at high elevations 
certain indigenous grass-land plants invade the corn crop only . 1 
The above distinctions in terms of individual species are slight ; if, 
however, the frequencies of some of the more abundantly occurring species 
are compared, it will be seen that the differences in the communities are 
more marked. 
The following species have higher frequencies under cereals than roots : 2 
Cotswolds. 
Pap aver R hoe as. 
Fumaria officinalis. 
Brassica arvensis. 
Silene Cucubalus. 
Lychnis alba . 
L. Githago. 
Scabiosa arvensis. 
Taraxacum officinale. 
Legousia hybrida. - 
Lithospermum arvense. 
Veronica hederaefolia. 
Polygonum Convolvulus. 
The following species tend to have higher frequencies under roots than 
cereals : 
Cotswolds. 
Capsella Bursa-pastoris. 
Senecio vidgaris. 
Lamium purpureum. 
Polygonum Persicaria. 
Atriplex patida. 
Euphorbia Helioscopia . 
It is also noteworthy that a number of species, although not necessarily 
1 See p. 171, section (d), species marked with a dagger. 
2 In districts where farmers sow cereals saved from their own stacks, the following weed seeds 
are frequent impurities : Lychnis Githago , Polygonum Persicaria , P. Convolvulus , Convolvulus 
arvensis , and Ruviex spp. 
Mid-Wales (below 800'). 
Sonchus oleraceus. 
Calamintha officinalis. 
Polygonum Persicaria. 
Atriplex patida. 
Mid-Wales (below 8oo'). 
Ranunculus repens. 
Brassica arvensis. 
Spergula arvensis. 
Chrysanthemum segetum. 
Rumex Ace to sella. 
