CHAPTER III 



THE GROWING PLANT 



Having now taken the plantlet out of the seed and hav- 

 ing estabHshed it as an independent organism, we may 

 next inquire how it secures its food and how it grows. 



57. Chlorophyll. — Soon after the plantlet emerges 

 from the seed-case, a green color appears in the parts 

 most exposed to light. This is due to the formation within 

 the cells of chlorophyll — the green coloring matter of 

 plants. Chlorophyll forms only in light, and when a 

 plant containing green leaves is kept for a time in the 

 dark, as when celery is banked up with earth, the chloro- 

 phyll disappears and the green parts become white. The 

 chlorophyll saturates definite particles of protoplasm, 

 called chlorophyll bodies, and since the cell-walls and 

 protoplasm are transparent in the younger cells, the 

 chlorophyll bodies give the parts containing them a green 

 color. Fig. 15 shows the distribution of the chlorophyll 

 bodies in the cells of a portion of a leaf of the beech. They 

 appear as minute globules, which in this case are mostly 

 located near the cell-walls. They are most numerous 

 near the upper surface of the leaf — the part most exposed 

 to the sun's rays. 



58. Formation of food. — No food can be formed with- 

 out chlorophyll. By the agency of chlorophyll, the 



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