on the Growth of Barley and Wheat in Water Cultures. 89 
also has a very marked action upon the relative rate of growth of roots and 
shoots, and this is well shown in the experiments under discussion. All the 
way through, the shoot responds more sharply than the root to the changes 
in food supply ; consequently, as the solution decreases in strength the ratio 
between the dry weights of shoots and roots also decreases ; in other words, 
the weights of the roots and shoots tend to approximate more closely as the 
supply of nutriment gets smaller, until in some cases with very dilute solu- 
tions the root is as heavy as, or even heavier than, the shoot (Table II). The 
change in ratio takes place always, whether the solutions are changed or not 
during growth, but it is most marked in those cases in which great starvation 
has ensued owing to the low concentrations not being renewed. It seems as 
though the plant makes every endeavour to supply itself with adequate 
nutriment, and as if, when the food supply is low, it strives to make as much 
root growth as possible so as to offer the greatest absorbing surface for 
whatever nutriment may be available. 
Shoot / Root Ratio. 
Series 
I. 
March 15-May 3. 
N 
N /5 
N/10 
N/20 
Solutions changed frequently . 
. 
2-691 
2-506 
2-431 
2-468 
,, ,, once 
. 
3-702 
2-731 
1-770 
1-548 
„ „ never . . 
• 
2-580 
2-149 
1-750 
1-174 
Series 
2. 
April 5- 
-May 24. 
N 
N /5 
N/10 
N/20 
Solutions changed frequently . 
. 
33 - 4 T 
2-956 
2.252 
1.876 
„ „ once . . 
. 
2-830 
2-288 
I * 79 I 
1-144 
,, „ never . . 
• 
2-630 
i-8oo 
1-285 
0-979 
Series 
3 * 
April 26-June 14. 
N 
N /5 
N/10 
N/20 
Solutions changed frequently . 
• 
3-892 
3 *ii 7 
2*835 
2-379 
,, ,, once . 
. 
2-297 
2-289 
1-946 
1-582 
„ ,, never . . 
. 
1-857 
1*336 
1-226 
1-039 
Table II. Showing the ratio between the shoots and roots of the 
barley-plants whose mean dry weights are given in Table I. 
Summary. 
When plants, such as barley and wheat, are grown in water cultures 
under favourable conditions, the concentration of the nutrient solution, up 
to a comparatively high strength, has a great effect upon the rate and 
amount of growth, even when the balance of the solution approximates 
to a constant level. Starvation effects, due to insufficient nutriment, are 
evident in much stronger concentrations than has been admitted by some 
