i6 



GROWTH AND WORK OF PLANTS 



the leaves become green. In germination the radicle emerges 

 from the micropylar end of the seed. The hypocotyl elongates 

 and forms a loop which pulls the leafy end of the stem and the 

 cotyledons from the ground (fig. 23). 



CONCLUSIONS. 



20. The seed. A seed is a plant structure composed of the 

 embryo plant surrounded by the seed coats which often enclose 

 food where this is not stored in some part of the 



embryo. The seed is capable, by the growth of 

 the embryo, of producing a plant similar to the 

 parent. 



The embryo is made up of the three principal 

 parts of the plant, the 

 root, stem and leaf, but 

 these parts are in a very 

 rudimentary form. 

 Squash, pea, bean, 

 castor bean and apple 

 seeds are examples of 

 clearly defined seeds.. The 

 "shell" of the squash or apple 

 seed or the membrane which 

 can be slipped off from a pea 

 or bean after being thoroughly 

 soaked in water, is made up of 

 the seed coats. The entire con- 

 tent of the squash or almond 

 seed is the embryo. 



21. Food stored in the 

 seed. Nearly all seeds have 

 food stored in them to furnish 

 nutriment for the embryo plant 

 from the time of germination 



until the seedling has established itself in the earth, where it 

 can obtain its food from the outside. In the squash, bean, pea, 



Fig. 24. 

 White-pine seedling casting seed coats. 



