318 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9. 
total dry weight was slightly greater in the plants grown in the dry atmos- 
phere. The total ash content was only slightly greater, 147 milligrams 
per culture in the plants grown in the dry atmosphere as compared with 
135 milligrams per culture in the plants grown in the humid atmosphere. 
The total ash expressed as percentage of dry weight was only about five 
percent less (ratio of dry to humid = 100 : 94.7) in the plants grown in the 
humid chamber than in those grown in the dry chamber. The ash, ex- 
pressed as percentage of green weight, was about fourteen percent less 
(ratio of dry to humid 100 : 86.4) in the plants grown in the humid 
chamber. 
Table i. Relation of Ash Content in Barley Plants to the Amount of Transpiration as 
Affected by a Diference in Atmospheric Humidity. Summer Series. 
Plants Grown 5 Weeks {August 4 to September 8, IQ20) 
Dry Chamber 
Humid Chamber 
Tops 
Roots 
Plants 
Tops 
Roots 
Plants 
No. of cultures averaged 
25 
25 
Green weight per culture (grams) 
H 
2.2 
8.7 
7.206 
2.067 
9.270 
Dry weight per culture (grams). 
.60 
.11 
.71 
.5854 
.1068 
.6922 
Total ash content per culture 
(grams) 
.125 
.022 
.147 
.116 
.019 
•135 
Ash content (percentage of green 
weight) 
1.92 
1. 00 
1.69 
1. 61 
.90 
1.46 
Ash content (percentage of dry 
19.63 
weight) 
20.7 
20.02 
20.63 
18.07 
19-54 
Total water transpired (cc). . . . 
170 
Water used per gram dry matter 
(cc.) 
492.96 
245-59 
Water used per gram ash con- 
tent (cc.) 
2,380.95 
1,259-25 
The data show that by increasing the atmospheric humidity the quan- 
tity of water transpired was reduced from 350 cubic centimeters to 170 
cubic centimeters per culture for the period of five weeks. This reduction 
in transpiration also correspondingly reduced the water requirement from 
492 to 245. The quantity of water transpired per gram of ash content 
found in the plants was also reduced to approximately one half when trans- 
piration was reduced. These data seem to check with those reported by 
Hasselbring (1914 a), Kiesselbach (1916), McLean (1919), and Curtis 
(1920), indicating that there is no direct relation between transpira- 
tion and the ash content in plants. 
The fact that the absolute quantity or percentage of ash is reduced but 
slightly when transpiration is reduced to less than one half seems significant 
evidence against the theory that there is a direct relation between trans- 
piration and the absorption of salts. Even the slightly greater ash content 
of the plants in the dry chamber seems to be determined by some factor 
other than the amount of water absorbed, namely food supply, which will 
