430 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
of tops to roots. Another fact indicated is that there is probably a critical 
concentration of solution beyond which the root will respond morphologically 
more or less sharply ; evidence for this is shown from the data that the longest 
roots were in the high-nitrate solution in Experiment I, which had a con- 
centration of 2,100 p. p.m., while with a concentration of 3,075 p. p.m. they 
are shortest and are otherwise different in form. 
Increase in Ratio of Tops to Roots at Different Stages of 
Maturity in Young Plants 
Table 5a shows the increase in the ratio of tops to roots, at different 
stages of maturity as the plants grew under the conditions of this experiment. 
This table shows results similar to those secured in Experiment I. 
Table 5. Experiment II {Barley); Behavior of Nitrates when Total Concentration is Reversed 
{Dry Weights in Grams) 
Sol 
la (Low Nitrate) 
Sol. II (Medium Nitrate) 
Sol. Ilia (High Nitrate) 
Tops 
Roots 
Tops 
Roots 
Tops 
Roots 
Tops 
Roots 
Tops 
Roots 
Tops 
Roots 
Series i, 
14 days 
•0437 
•0559 
.0587 
.0650 
•0135 
.0183 
.0182 
.0182 
3-23 
3-05 
3-23 
3-57 
.0883 
.0758 
.0740 
.0710 
.0200 
.0188 
.0178 
.0164 
4.41 
4-03 
4-15 
4-34 
.0632 
.0654 
,0624 
.0624 
.0163 
.0146 
.0160 
.0150 
3- 94 
4- 47 
3.90 
4.16 
Total . . 
•2233 
.0682 
.3091 
.0730 
.2534 
.0619 
Mean . . 
3.27 ±.073 
4.32=t.o58' 
• 
4.i2±.o88 
Diffprenre 
Hi 
3-h Nitrate — Low 
Nitrate 
= .8=; -4- TT^. 
Series 2, 
28 days 
.1500 
.1430 
•1733 
.1462 
•0313 
.0263 
.0346 
.0340 
4.19 
5-43 
5.00 
4-30 
.1841 
.2040 
.1643 
.2122 
.0322 
.0320 
.0263 
.0329 
572 
6.38 
6.21 
6.45 
.1867 
.1792 
.2085 
•1795 
.0290 
.0270 
.0295 
.0290 
6.44 
6.64 
7.07 
6.23 
Total . . 
.6123 
.1262 
.7646 
.1244 
.7539 
•II45 
Mean. . 
4-88±.i57 
6.i9ifc.iii 
6.59±.i22 
Difference High Nitrate — Low Nitrate = 1.71 it .199. 
Series 3, 
40 days 
.3310 
.2586 
.2810 
•3308 
.0707 
•0577 
.0600 
.0600 
4.70 
4.48 
4.68 
5-51 
•3370 
•4529 
.4917 
•3938 
.0478 
.0651 
•0715 
.0622 
7-05 
6.96 
6.88 
6.33 
.4020 
.4616 
.4213 
•5308 
.0526 
•0525 
.0562 
.0671 
7.64 
8.79 
7.49 
7.91 
Total . . 
1. 2014 
.2484 
- 
1-6754 
.2466 
1.8157 
.2284 
Mean. . 
4.84^.153 
6.8i±.io8 
7.95±.i22 
Difference 
High Nitrate - Low Nitrate =3.11 it .195. 
