140 FIELD, FOREST AND FARM 



compact ; why delicate seeds should be covered with 

 very little earth or even simply sown on the surface 

 of the moist ground; and, finally, why ground on 

 being broken often becomes covered with fresh veg- 

 etation from the sprouting of seeds that have for 

 years lain dormant in the soil, needing only to be 

 stirred up and brought into contact with the air in 

 order to germinate. 



"Under like conditions of temperature, moisture, 

 and air, by no means all seeds require the same 

 length of time for germinating. Common garden 

 cress germinates in about two days. Spinach, tur- 

 nips, and beans take three days to come up ; lettuce, 

 four; melons and pumpkins, five; cereals, about a 

 week. Two years and sometimes more are needed 

 by the rose-bush, the hawthorn, and various stone- 

 fruit trees. Generally seeds with thick and hard 

 shells are slow in germinating on account of the ob- 

 stacle they oppose to the penetration of moisture. 

 Finally, when sown fresh, immediately after coming 

 to maturity, seeds germinate quicker than when old, 

 because old seeds have to recover by a prolonged so- 

 journ in the ground the moisture lost through pro- 

 longed drying. 



"According to their kind, seeds retain for a longer 

 or shorter period their power of germinating; but 

 why this vitality is more enduring in one instance 

 and less so in another, we cannot tell. Neither the 

 bulk of the seed nor the character of its outside cov- 

 erings, nor the presence or absence of a perisperm, 

 appears to decide its longevity. Such and such a 



