the Soils on which they grow . 163 
Polygonaceae 
Rumex Acetosa 
sand 
Euphorbiaceae 
Euphorbia exigua 
various 
>> 
„ helioscopia 
sand 
>> 
„ Peplus 
various 
Urticaceae 
Urtica dioica 
sand 
Dioscoreaceae 
Tamus communis 
chalk 
Liliaceae 
Allium vineale 
heavy clay 
Gramineae 
Bromus arvensis 
chalk 
») 
„ asper 
)) 
» 
Holcus lanatus 
sand and clay 
r 
Hordeum pratense 
heavy clay 
jj 
Lolium perenne 
various 
V 
Phleum pratense 
3 
Poa pratensis 
gravelly loam 
Points of Interest . 
1. While the nature of the soil plays such an important part in deter- 
mining the local weed flora, the character of the crop, generally speaking, is 
a matter of indifference. The one exception to this rule is in the case 
of seed crops — clover, lucerne, sainfoin, trefoil. Many weeds, though they 
are to be found with every other crop, are entirely absent or very rare with 
seeds. This may be due to the difference in habit, as the Leguminous 
plants cover the ground so closely with such a dense mass of herbage that 
probably many weeds are choked out. One or two species, especially 
Geranium sp., Cerastium vulgatum , and Sherardia arvensis , are almost 
entirely confined to such crops, and it is possible that these weeds are not 
indigenous, but are introduced with the seeds of the crop. 
A very few species are practically confined to cereal crops : — 
Anthemis Cotula Centaurea nigra 
Brassica alba Poa annua 
„ S inapis 
Weeds absent or very rare in seed crops . 
Agrostis stolonifera 
Anagallis arvensis 
Chenopodium album 
Equisetum arvense 
Galium Aparine 
Gnaphalium uliginosum 
Mentha arvensis 
Plantago major 
Poa annua 
Polygonum aviculare 
,, Convolvulus 
„ Persicaria 
Ranunculus arvensis 
Scandix Pecten 
Spergula arvensis 
Stellaria media 
M 2 
