CONDITIONS OF GERMINATION 207 
affect seeds unfavorably if they are not too moist. 
The warmth of the soil, essential to germination, can- 
not well be controlled by the farmer; and planting 
must, therefore, be done in seasons when, from past 
experience, it is probable that the temperature is and 
will remain in the neighborhood of the best degree 
for germination. More heat is required to raise the 
temperature of wet soils; therefore, seeds will gener- 
ally germinate more slowly in wet than in dry soils, as 
is illustrated in the rapid germination often observed 
in well-tilled dry-farm soils. Consequently, it is 
safer at a low temperature to sow in dry soils than 
in wet ones. Dark soils absorb heat more rapidly 
than lighter colored ones, and under the same condi- 
tions of temperature germination is therefore more 
likely to go on rapidly in dark colored soils. Over 
the dry-farm territory the soils are generally light 
colored, which would tend to delay germination. 
The incorporation of organic matter with the soil, 
which tends to darken the soil, has a slight though 
important bearing on germination as well as on the 
general fertility of the soil, and should be made an 
important dry-farm practice. Meanwhile, the tem- 
perature of the soil depends almost wholly upon the 
prevailing temperature conditions in the district and 
is not to any material degree under the control of the 
farmer. 
A sufficient supply of oxygen in the soil is indis- 
pensable to germination. Oxygen, as is well known, 
