Wheat tinder Different Conditions of Growth. 551 
In this case, again, maximum root development appeared to be attained 
almost simultaneously with the emergence of the ears from the sheaths, 
though with superphosphate this maximum was reached earlier, exactly as 
occurred with barley. With no manure, on the contrary, root growth 
continued after the ears had emerged, even though the latter event was 
somewhat later than in manured plants. As the two cereals followed one 
another so closely, it seems probable that the same explanation as to 
association of purely vegetable growth with increase of root weight will 
hold good in both instances. 
In wheat the shoot/root ratio appeared to fall for about nine weeks, and 
though a slight rise took place in the next fortnight no rapid increase in 
Table VI. 
Shoot / Root Ratio. Wheat. 
Super- 
Super- 
Date . 
Unmanured. 
Sodium 
Super- 
phosphate + 
phosphate + 
nitrate . 
phosphate. 
Sodium 
Potassium 
nitrate. 
sulphate. 
April 13 
1.32 
1-22 
1.97 
1.91 
2-16 
i-i8 
I * 5 I 
2-04 
2.23 
1.72 
April 2 7 
0-90 
1. 16 
1. 01 
1.56 
1.42 
1-24 
I -00 
1.48 
1-47 
1.66 
May 11 
1. 18 
i -45 
I, 59 
1-84 
1.65 
1.05 
1. 16 
1.92 
1.25 
1.80 
June 1 
2-64 
' 2-57 
1.88 
3.21 
2.25 
June 15 
2-24 
i-8o 
2-09 
2.45 
1.84 
3- J 9 
3-45 
3-93 
3 -i 9 
3 - 4 i 
2.66 
3.66 
2*1 I 
4.22 
3.28 
July 13 
4.28 
5-70 
4.63 
8.60 
6-75 
4.78 
6.63 
5*05 
5.92 
4-38 
August 24 
9-01 
10.95 
14-34 
13-43 
12-66 
13.24 
14.56 
7-37 
19-54 
— 
the ratio occurred till after this time. The effect of the superphosphate in 
increasing the relative proportion of shoot to root was evident at a very 
early date, all the ratios for the first 11 weeks being above those for 
unmanured and nitrate plants, in which it was not much above unity. As 
time went on the effect of the nitrate, especially when combined with 
superphosphate, became more marked, showing that the shoot increased 
relatively more rapidly than the root. The unmanured and superphos- 
phate plants, however, showed almost identical shoot/root ratios after the 
earlier period was past, indicating that the phosphate gave equal encourage- 
ment to both organs when the initial stages of growth were over (Fig. 4 
and Table VI). The change in the curve of the shoot/root ratio was less 
sharply marked in wheat than in barley, and took place considerably earlier. 
This may be accounted for by the fact that wheat is typically autumn sown, 
is used to coping with unfavourable weather conditions, and can start 
into active growth with comparatively low temperature. The change in the 
shoot/root ratio of wheat began as soon as the mean maximum temperature 
