56 



PLANT GROWTH AND NUTRITION 



Developed fiypocof /I- 



stages in the germination of the kidney bean. 



If some beans are planted so that we can make a record of their 



growth, we shall find the first signs of germination to be the break- 

 ing of the testa and the 

 pushing outward of the 

 hypocotyl to form the 

 first root, which grows 

 downward. A later 

 stage shows the hypoco- 

 tyl forming an arch and 

 dragging the bulky 

 cotyledons after it. The 

 stem, as soon as it is 

 released from the 

 ground, straightens up. 

 The cotyledons open, 

 and between them the 

 budlike plumule or epi- 



cotyl grows upward, forming the first true leaves and all of the 



stem above the cotyledons. 



As growth continues, we 



notice that the cotyledons 



become smaller and smaller, 



until their food contents are 



completely absorbed into 



the young plant. The young 



plant now has roots and 



leaves and is able to care 



for itself and may be said 



to have passed through the 



stages of germination. 

 What makes an Engine 



go. — If we examine the 



sawdust or soil in which the 



seeds are growing, we find 



it forced up by the growing 



seeds. Evidently work was 



done ; in other words, energy was released by the /Seeds. A 



familiar example of release of energy is seen in an engme. Coal 



Experiment to show the function of the 

 cotyledons of the pea: a, plant with both 

 cotyledons, b, with one removed, c, with both 

 removed. A, at end of one week; B, at end 

 of three weeks. 



