326 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
centage of ash in the whole plants was still slightly greater in the plants 
having the greater dry weight. 
This slightly greater relative increase in the ash weight than in the dry 
weight seems to indicate that when a slightly greater quantity of food is 
available it is used for additional growth, perhaps largely in building up 
additional protoplasm. The addition of protoplasm, which is relatively 
higher in salts than non-protoplasmic structures, might increase the per- 
Table 9. Relation between the Increase in Dry Weight and Ash in Barley Plants 
Dry-Humid. . . 
Summer Series 
(From table 
I) 
Tops. 
Roots . 
Plants. 
Dry Weight 
in Grams 
Ash Weight 
in Grams 
Percentage of Ash 
Difference in 
Percentage of Ash 
Dry 
Humid 
Dry 
Humid 
Dry 
Humid 
.60 
.11 
.71 
.5854 
.1068 
.6922 
.125 
.022 
.147 
.116 
.019 
.135 
20.74 
20.02 
20.63 
19.63 
18.07 
19-54 
I. II ± .037 
1.95 ± .035 
1.09 ± .027 
Light 
Shade 
Light 
Shade 
Light 
Shade 
Light-Shade. . 
Summer Series 
(From table 
2) 
Tops. . 
Roots. 
Plants. 
1-235 
.2897 
1-525 
-509 
.085 
•594 
.2335 
.0885 
.322 
.1036 
.0173 
.1209 
18.91 
30.55 
21.13 
20.34 
20.35 
20.34 
- 1.43 ± .032 
10.20 =b .064 
.79 ± .029 
Light 
Shade 
Light 
Shade 
Light 
Shade 
Light-Shade. . 
Winter Series. . 
(From table 
5) 
Tops . . 
Roots . 
Plants. 
-765 
.150 
. -915 
.408 
.052 
.460 
-151 
.031 
.182 
.078 
.009 
.087 
19.70 
20.51 
19-83 
19.56 
17.21 
19.30 
.14 d= .034 
3.30 ± -053 
-53 ± -031 
centage of ash slightly. If, on the other hand, food is produced in excess, 
as was evidently the case in the tops of the plants grown in the sunlight, a 
point is soon reached at which the utilization of foods and inorganic salts 
in the building of protoplasm is limited. The surplus food may then be 
used in the building of cell-wall material, or it may be stored in some other 
form. Since cell walls and storage products in plants are usually low in 
ash content, it is evident that any great increase in the production of these 
over the production of protoplasm would lower the percentage of ash in the 
dry matter. 
The last column of table 9 presents the differences in the percentages 
of ash in the tops, roots, and total plants between the high- and low-trans- 
piring plants. In every case the relative increase of ash was higher in the 
roots than in the tops. Those roots showing the greatest relative increase 
in ash content are those which also show the greatest increase in dry matter. 
