The Effect of Weeds upon Cereal Crops. 63 
Woburn Soil. 
TOTAL 
DRY WEIGHTS OF CROPS FROM SIX 
POTS. 
Crop. 
Weed. 
Grams. 
Grams. 
Papaver + Papaver 
74.3 
73.3 
Wheat + Papaver 
10.1 
99.4 
Wheat +Wheat 
76.7 
W heat + Spergula 
32.4 
Spergula + Spergula 
106.4 
AVERAGE DRY WEIGHTS OF SHOOTS. 
CROP. 
WEED. 
Per plant. 
Per 
single sowing. 
Per single sowing. 
Grams. 
Grams. 
Grams. 
Papaver+Papaver 
6.19 
3.055 
12.22 
Wheat + Papaver 
1.68 
2.07 
8.28 
Wheat + Wheat • 
3.195 
12.78 
Wheat + Spergula 
5.4 
Spergula +Spergula 
8.87 
Wheat and Papaver. 
The results were similar to those obtained in the previous 
experiments. The poppy grown with wheat was far shorter and 
less developed than that grown alone, reaching a height of 14—23 
cms. against 33—58 cms., this poorer development being associated 
with a heavy drop in dry weight. The wheat, again as before, was 
much stronger when in conjunction with the poppy, the average 
dry weight of the plants being much heavier than when grown 
alone. 
Wheat and Spergula. 
Spurrey was growing on a soil specially well adapted to it, as 
it is one of the natural weeds on the light sandy soil at Woburn. 
Consequently the plants grown by themselves made good growth, 
reaching a height of 33—42 cms., and making much weight. In 
conjunction with wheat the plants were shorter, 16—40 cms., but 
although the development was not so good as in the absence of 
wheat, still the drop in dry weight was far less marked than in most 
of the experiments. In spite of this relatively good growth of the 
weed, the wheat grown with it again made a very heavy average 
weight when compared with that grown alone. 
