122 
Hellriegel’s experiments gave 80 to 60 and sometimes 40 per cent, 
Fittbogen’s gave 40 to 30 per cent, Wollny’s gave 80 to 60 per cent 
of moisture for the maximum harvest. These differences undoubt- 
edly arose, at least in part, from differences in richness of the soil, 
the closeness of the plants, and differences in the sunshine and wind. 
These results are therefore in general only relative, and justify us 
in saying that the best crops are obtainable when the earth contains 
from 40 to 80 per cent of its maximum capacity for water and that 
the ‘percentage is higher in proportion as the soil is richer; as the 
plants are closer; as the leaves of the plants are broader; as the 
sunshine, the dryness of the air, and the velocity of the wind are 
greater; and as the barometric pressure is less, since all these increase 
the useful evaporation from the leaves and the wasteful evaporation 
from the soil. 
The growth of the auxiliary organs was shown by Fittbogen, who 
gives the weight of the organic matter as determined by burning the 
well-washed roots, and is also shown by Haberlandt by the weights 
of the roots and stubble. Their measures are given in the following 
tables: 
FITTBOGEN’S EXPERIMENTS. 
Organic 
Moisture} matter 
inthe | lost by 
soil. burn- 
ing. 
Per cent. mg. 
80-60 470 
60-40 | 429 
40-30 | 440 
30-20 359 
20-10 109 | © 
HABERLANDT’S EXPERIMENTS. 
Weight 
of roots 
Water eal 
stubble. 
ce. Gram. 
24, 800 5.35 
14, 400 3.2 
6, 200 2.9 
