Brenchley. — The Weeds of Arable Land. III. 157 
opportunity for a thorough cleaning of the land with cultivator and hoe, so 
many species which cannot withstand such drastic treatment tend to be 
conspicuous by their absence among roots. The barley and oats make 
a fair start on clean ground, and if the seed crop of clover, &c., is put 
down with the grain and makes fair growth, the weeds are very few in 
number and variety, as they have no chance to get a fair start in life before 
they are smothered out of existence. The seed crops offer quite different 
conditions. No cultivation is possible among such crops as clover and 
lucerne, so any weed seeds in the soil or introduced with the ‘ seeds ’ have 
the opportunity to germinate and flourish undisturbed if only they can com- 
pete successfully with the overshadowing of the crop ; but many species fail 
utterly in doing this, and so are generally absent from seed crops, while 
others seem to make a speciality of growing under such conditions. 
For working purposes it has proved necessary to divide up the seed 
crops into two classes, as the weed floras are frequently distinctive : 
‘ Seeds ’ — clover, temporary pasture, grasses. 
‘ Legumes ’ — peas, beans, lucerne, sainfoin, lupins. 
In the 1912 season some plants were found to be absent from seed and 
from root crops, while a few others were nearly always associated with 
cereals alone or with cereals and roots. 
Weeds absent or 
Agropyron repens 
Agrostis stolonifera 
Alopecurus myosuroides 
Chenopodium album 
Erysimum cheiranthoides 
Galium Aparine 
Gnaphalium uliginosum 
Legousia hybrida 
Poa annua 
Polygonum aviculare 
Weeds absent or 
Aethusa Cynapium 
Alchemilla arvensis 
Alopecurus myosuroides 
Anthemis arvensis 
Bartsia Odontites 
Beilis perennis 
Cerastium vulgatum 
Cichorium Intybus 
Crepis virens 
rare in seed crops. 
Polygonum Convolvulus 
„ Persicaria 
Rumex obtusifolius 
Scandix Pecten-veneris 
Silene inflata 
Spergula arvensis 
Stellaria media 
Taraxacum vulgare 
Veronica hederaefolia 
rare in root crops. 
Daucus Carota 
Echium vulgare 
Erophila verna 
Euphorbia exigua 
Holcus lanatus 
Lychnis Githago 
Lycopsis arvensis 
Matricaria Chamomilla 
„ inodora 
very 
very 
