24 seeds: structure and germination 



structure for changing, absorbing, and transferring this reserve- 

 food to the growing parts which need it. 



Ex. 14. — Note the softening of the endosperm in germinated wheat grains 

 and its decreased amount after seedlings have grown considerably. 



Remove the embryos from well-soaked grains, and grow them without 

 the endosperm on damp blotting-paper. Allow ordinary uninjured grains to 

 grow with them. Both the embryos in the grains and those removed from 

 the grains develop, but there is a great difference in the results after a few 

 days. 



15. The store of reserve-food on which the young plant 

 depends for its early development is sufficient to enable it 

 to form a root, stem, and several leaves, as is evident when 

 seeds are allowed to germinate upon damp flannel or blotting- 

 paper, from which nothing but water is absorbed. 



No food-materials or manures are needed for this primary 

 development, and seeds germinate and the seedlings grow for 

 a considerable time as well in poor soil or sand as in good 

 rich ground. As soon as the reserve store is exhausted hunger 

 becomes apparent, and unless the plants are then supplied with 

 suitable nutriment from the soil and air, and are also placed 

 under conditions favourable for growth, weakness and death 

 are likely to occur. 



Among the larger seeds, such as beans and peas, where there 

 is an abundant store of reserve-food, the young seedlings begin to 

 manufacture food for themselves from materials absorbed from 

 the soil and air, long before their reserve is exhausted. In 

 small seeds the reserve is sometimes almost consumed before 

 the roots and leaves are sufficiently developed to carry on 

 their work properly, in which cases a more or less temporary 

 starvation and check to growth ensues. Especially does this 

 happen when seeds are sown too deeply, for a large amount 

 of food is then used in the production of a stem long enough 

 to lift the leaves up into the air. 



