104 GERMINATION. 



species of Hieracium from seeds which had been in his herbarima 

 upwards of fifty years. Desmonlins has recorded an instance of the 

 opening of ancient tombs, in which seeds were found, and on being 

 planted they produced species of Scabiosa and Heliotropium. And 

 many more such cases are on record, establishing conclusively that, 

 under favourable conditions, the vitality of seeds is preserved for 

 indefinite periods. 



Warmth, moisture, and an excess of oxygen, but especially 

 warmth and moisture, while they are the greatest causes of 

 germination, are probably, on that same account, the chief 

 causes of death. It seems as if seeds remain dormant so long 

 as the proportion of carbon peculiar to them is undiminished ; 

 water is decomposed by their vital force ; and it is bslieved that 

 its oxygen, combining with the carbon, forms carbonic acid, 

 which is given off. The effect of access of water is, therefore, 

 to rob seeds of their carbon ; and the effect of destroying their 

 carbon is to deprive them of the principal means which they 

 possess of preserving their vitality. 



Be this as it may, it is incontestable that as scon as seeds begin to 

 germinate, their vitality is exhausted and they perish, unless the seed 

 is in a condition to continue its growth by obtaining suflSoient food from 

 surrounding media. 



Although a seed, if fully formed, is in all cases capable of 

 perpetuating its race, yet there is a difference in the degree to 

 which this capability extends. All seeds wiU not equally 

 produce vigorous seedlings: but the healthiness of the new 

 plant will correspond with that of the seed from which it 

 sprang. For this reason, it is not sufficient to sow a seed to 

 obtain a given plant : but, in all cases where any importance is 

 attached to the result, the' plumpest and heaviest seeds should 

 be selected, if the gi'eatest vigour is required in the seedling; 

 and feeble or less perfectly formed seeds, when it is desirable 

 to check natural luxuriance. It is apparently for this reason, 

 that old Melon seed is preferred to new ; for the latter would 

 give birth to plants too luxuriant for the small space in which 

 the Melon can be cultivated, under the artificial circumstances 

 required in this country. 



