7 1 
The Effect of Weeds upon Cereal Crops . 
The single sown Papaver made good heavy growth ; the plants 
were well developed with big flower buds, and were stronger than 
those grown in association with barley, though the difference was 
not very strongly marked. With double sowing the individuals 
were decidedly weaker, though the total growth seemed greater 
than with single sowing. All these observations were fully borne 
out by the dry weights. 
Barley and Spergula. 
The Spergula was more harmful to the associated barley than 
was barley itself, though the barley grown with this seed was 
rather stronger at harvest than that grown with Papaver. The 
competition of barley or Spergula with Spergula was very equal, as 
the total growth per single sowing in both cases was practically 
identical. When free from competition Spergula made far more 
growth, being more than 65 per cent, heavier in dry weight. 
Rothamsted Soil. 
TOTAL DRY WEIGHT OF CROPS FROM SIX POTS. 
Crop. 
Weed. 
Grams. 
Grams. 
Alopecurus 
87.94 
Alopecurus + Alopecurus 
101.57 
113.24 
Barley + Alopecurus 
14.70 
126.06 
Barley 
38.86 
Barley+Barley 
42.89 
Barley + Brassica 
62.76 
Brassica + Brassica 
60.34 
Brassica 
92.28 
AVERAGE DRY WEIGHTS OF SHOOTS. 
Crop. 
Weed. 
Per 
plant. 
Per 
single sowing. 
Per single sowing. 
Grams. 
Grams. 
Grams. 
Alopecurus 
14.66 
Alopecurus + Alopecurus 
8.45 
4.72 
18.87 
Barley + Alopecurus 
2.45 
5.25 
21.01 
Barley 
2.43 
9.72 
Barley + Barley 
1.79 
7.15 
Barley + Brassica 
10.46 
Brassica + Brassica 
5.03 
Brassica 
15.38 
