STRUCTURE AND GERMINATION OF SEEDS 25 



determine the uses of the structures found in a Bean seed. 

 Soak a number of dry seeds in water for a day, and then 

 sow several in a pot of damp coco-nut fibre, sand, or saw- 

 dust. In a few days remove some of them carefully, 

 allowing the rest to continue their growth. Note what 

 has happened. Which structure is the first to emerge from 

 the seed radicle or plumule ? As the radicle emerges you 

 will see that it bursts through the skin near the micropyle. 

 Later on, look for the plumule as it pushes its way through 

 the soil. Of what form is it ? Do you see any advantage 

 in this mode of emergence ? 



At the end of the crook-like plumule note the tender 

 young leaves, observing that they are carried upwards 

 as the stem grows, with little risk of injury, and that when 

 well above the surface the plumule grows more quickly on 

 the under side than on the upper, and so straightens itself. 

 The leaves expand, new ones appear in succession, and in 

 time buds form in their axils, which grow into leafy shoots 

 similar to that from which they spring. In cases where 

 the plumule has been injured, note that buds arise in the 

 axils of the cotyledons. 



Although a seedling is able to obtain little or no food 

 from the coco-nut fibre, sawdust, or sand, for some time 

 it continues to grow vigorously, increasing its roots and 

 enlarging its stem and leaves. Upon what is the plant 

 feeding ? Where does the material come from ? If we 

 examine an older Bean seedling, we find that the cotyledons 

 remain below ground and do not emerge from the seed- 

 coat, but gradually lose their contents and shrivel up as 

 the plant grows : i.e. the cotyledons, at first swollen with 

 starchy and other food, provide the materials upon which 

 the seedling feeds and grows in the earlier period of its life. 



In the Kidney-Bean or Scarlet -Runner the cotyledons, 

 though fleshy, come above ground and turn green (Fig. 10). 



Hypogeal and epigeal germination. Sow seeds of Mustard 



