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 ccjndi- 

 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, 



