Chapter 6. 



SEEDS AND SEEDLINGS. 



Vitality and longevity of seeds. Conditions favouring germi- 

 nation. Seedlings. Variation. Natural and artificial selection. 

 Sports or mutations. Hybrids and the laws of heredity. 



Ripe seeds are surrounded by a hard seed coat which is 

 more or less impervious and prevents complete drying up 

 of the embryonic plant within the seed. The more re- 

 sistant the coat the longer the seed can preserve its vitality. 

 The seeds of some plants germinate almost immediately 

 they are mature, but most of them are adapted for and 

 require a period of rest. During that time it is necessary 

 to keep them dry and fairly cool. Under such conditions 

 they can preserve their power of germination for some 

 years, though a certain number even of resistant seeds will 

 die. It is also more difficult to germinate old seeds, owing 

 probably to the drying of the seed coat, as well as to 

 changes which have taken place in the living cells of the 

 seed. When kept dry little alteration takes place 

 internally, and the seed can remain dormant, practically 

 no loss of matter taking place by respiration. For what 

 length of time this suspension of animation can last is not 

 definitely ascertained, but we may say with certainty that 

 we have no proof that seeds which have lain dormant for 

 a thousand years or more, .like those which have been, taken 

 from Egyptian mummy cases, can be germinated. ' That 

 so-called mummy wheat and mummy peas have been 

 originally obtained from Egyptian mummies must be re- 

 garded as purely legendary. Accurate investigations 



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