262 SECTIONAL ADDRESSES. 
quite apart from any increase in quantity—when treated with phosphates. 
Potatoes are considerably influenced by manuring ; increasing the supply 
of potassium influences the composition of the tubers and also that much 
more impalpable quality—the cook’s estimate of the value of the potato ; 
while we have found at Rothamsted that a high-class cook discriminated 
between potatoes fertilised with sulphate of potash and those fertilised with 
muriate of potash, giving preference to the former. 
Grain is more difficult to alter by changes in environmental condi- 
tions; indeed, it appears that the plant tends to produce seed of substan- 
tially the same composition whatever its treatment—with the important 
exception of variation in moisture supply. Mr. Shutt has explored the 
possibilities of altering the character of the wheat grain by varying the soil 
conditions, and finds that increases in soil moisture decrease the nitrogen 
in the grain. Similar results have been obtained in the United States. 
On the other hand, in England the reverse seems to hold, at any rate 
for barley. This crop is being fully investigated at the present time under 
the Research Scheme of the Institute of Brewing, because of its importance 
in the preparation of what is still Britain’s national beverage. Increased 
moisture supply increases the percentage of nitrogen in the grain, and so 
also does increased nitrogen supply, though to a much less extent; on 
the other hand, both potassic and phosphatic fertilisers may decrease the 
percentage of nitrogen, though they do not always do so; the laws regu- 
lating their action are unknown to us. 
The practical importance of these problems of regulating the composi- 
tion of the plant lies in the fact that the farmer can control his fertiliser 
supply, and also to some extent his moisture supply, so that it les within 
his power to effect some change should he wish to do so. 
The following are the nitrogen contents and the valuations of barley 
grown in the same season from the same lot of seed on farms only a few 
miles apart :— 
Effect of Moisture. 
Drier soil Moist land 
Nitrogen percent. in grain... .. 144 1:80 
Valuation per quarter of 448 lb. .. 52s. 5d. 41s. 6d. 
Effect of Nutrients. 
No nitrogenous Nitrogenous 
manure manure 
Nitrogen percent. in grain... Be sas) 1-464 
Valuation per quarter of 448 lb. .. 53s. 52s. 
At present we know but little about the matter and we are not in a 
position to advise the farmer as to how he may use these facts to the full 
advantage. The complete study of the problem necessitates the co-opera- 
tion of a plant physiologist. 
There is another direction also in which alterations in the plant would 
be of great value if only we knew with certainty how to bring them about. 
In agricultural science one sometimes thinks only of the crop and the ~ 
factors that affect its growth. But in agricultural practice there is often 
another partner in the concern: a pest or parasite causing disease. The 
amount of damage done by pests and diseases to agricultural crops is 
