THE FREE WATER OF THE SOIL, 215 
The waterings were made simultaneously at the moment 
when all the water previously given to No. 1 was ab- 
sorbed by the soil. During the 67 days of the experi- 
ment the plants were watered 17 times. The subjoined 
table gives the results: 
Weight of PP ht of 
Sresh Crops in ps in| Number of Liters of 
No. of pot. grams. ered : Seeds. water used. 
STRAW. | SEEDS, 
1 27.99 4.52 1.68 111 25.0 
2 65.05 8.47 5.47 283 12.5 
3 24.95 4.55 1.73 93 6.25 
4 9.98 1.41 0.52 37 3.12 
5 2.30 6.30 0.09 12 1.56 
‘The experiment demonstrates that the quantity of 
water supplied to a plant has a decided effect upon the 
yield. Pot No. 2 was most favorably situated in this re- 
spect. No. 1 had a surplus of water and the other pots. 
received too little. The experiment does not teach what 
proportion of water in the soil was most advantageous, 
for neither the weight of the soil nor the size of the pot 
is mentioned. 
Hellriegel (Chem. Ackersmann, 1868, p. 15) experiment- 
ed with wheat, rye, and oats, in a pure sand mixed with a 
sufficiency of plant-food. The sand when saturated with 
water contained 25°|, of the liquid. The following table 
gives further particulars of his experiments and the re- 
sults. The weights are grams, 
‘WATER IN THE SOIL. YIELD OF WHEAT.| YIELD OF RYE. | YIELD OF OATS. 
In per cent) Straw Straw Straw 
In per centiof retentive) and and and 
of Soil. power. Chaff. | Grain. | Chaff. | Grain. | Chaff. | Grain. 
24-5 10-20 7.0 2.8 8.3 3.9 4.2 1.8 
5 -10 20-40 15.1 8.4 11.8 8.1 11.8 78 
10 -15 40-60 21.4 10.8 15.1 10.3 13.9 10.9 
15 -20 60-80 23.3 11.4 16.4 10.3 15.8 11.8 
In each case the proportion of water in the soil was 
preserved within the limits given in the first column of 
the table, throughout the entire period of growth. It is 
seen that in this sandy soil 10-15 per cent of water ena- 
