SEEDS AND SEEDLINGS 19 



swollen out with nutrient substances. This is the arrange- 

 ment in seeds like the Peanut, Walnut, and Chestnut ; 

 the edible kernel is really a rudimentary plant. 



13. The seed food of embryonic plants consists chiefly 

 of starch, fat, sugar, and in smaller quantities proteid 

 substances ; that is, substances resembling the white of 

 egg and the curd of milk. Transformed by the growing 

 embryo and seedling into living substance and frame- 

 work, with the addition of water alone, these concentrated 

 formative matters may enable the young plant to grow to 

 Inany times the size of the original seed. 



14. The resting state. The germ may remain long 

 dormant in the seed. Its condition is then like that of 

 the buds of trees and the underground bulbs of herbaceous 

 plants in winter. Life sleeps, so to speak ; and the living 

 parts can endure extremes of dryness, cold, and so on, 

 which they are unable to bear in their more active periods. 

 Thus the embryo passes uninjured through change of sea- 

 sons that would cause the death of a seedling. Dormant 

 and well protected, it may be carried to great distances. 

 If at first unfavorably lodged, the seed may long await a 

 change of circumstances. When a forest is cleared away, 

 a great variety of field plants at once spring up, doubtless 

 from seed deposited in the soil long before. 



15. Retention of vitality De Candolle kept seeds of 



many kinds for fifteen years, when those of a few species 

 germinated. In another case the known age of seeds 

 which still kept their vitality was forty-three years. 1 On 

 the other hand, certain seeds must be planted as soon as 

 separated from the fruit. 



16. The conditions of germination. When the slow 

 inward changes of the dormant period have fully pre- 

 pared the seed, or when ripeness has come, even without 

 a resting stage, germination will begin, if a few neces- 

 sary conditions are fulfilled. There must be water, 

 warmth, and oxygen. 



1 The stories of the germination of seeds from mummy cases are with- 

 out foundation. 



