72 
Winifred E Brenchley. 
Barley and Alopecurus. 
In this case the harmful effects of the barley upon Alopecurus 
was far greater than that of Alopecurus upon barley. The drop in 
weight of barley due to the competition of the associated weed was 
less marked than with any of the other weeds used, whether in 
Rothamsted or Woburn soil. The Alopecurus was evidently far 
more affected by competition. It reduced its own production of 
dry matter by about 40 per cent., and the competition of barley 
caused a drop of over 80 per cent. The latter result serves to 
corroborate the idea suggested by the 1915 experiments that 
Alopecurus can only flourish and become a serious competitor of a 
cereal crop when it is able to germinate at its own special time and 
to get a firm undisturbed hold on the soil before the crop has had 
a chance of attaining any size. Consequently Alopecurus is not 
to be expected to be a serious competitor with spring crops which 
start right away and make strong growth within a comparatively 
short time. 
Barley and Brassica. 
The Brassica behaved rather differently this season. All the 
way through the experiment that sown with barley looked decidedly 
stronger than the double sown Brassica, though it was weaker than 
that sown grown alone in single sowing. With double sowing the 
weight dropped to ^ that of the single sown plants, indicating a 
more vital competition between Brassica and Brassica than between 
Brassica and barley for this experiment. 
WATER CULTURE EXPERIMENTS. 
Pot experiments did not give any indication that toxic 
excretions from the weed roots were affecting the growth of the 
crops, so an initial attempt was made in 1915 to throw some light 
on this question by a series of water cultures, and though the 
immediate object was not attained, still some interesting results 
were forthcoming. 
A fairly strong food solution was used, containing 
1 gram. Potassium nitrate. 
0-5 ,, Calcium sulphate. 
0-5 „ Magnesium sulphate. 
0*5 „ Sodium chloride. 
0 5 „ Potassium dihydrogen phosphate. 
0'04 „ Ferric chloride. 
Distilled water to make up one litre, 
