42 



Principles of Plant Culture. 



pears 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 chlorophyll 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 



Fig. 1.5. Showing cross-section througli leaf of Fagus sylvatica. 

 C chloropliyll bodies ; Ep epidermis of upper surface of leaf ; Ep" 

 epidermis of lower surface ; K cells containing crystals ; PI palisade 

 layer ;F vascular bundle ; St stomate ; I spaces between the cells 

 (intercellular spaces). Highly magnified. (After Strasburger.) 



containing them a green color. Fig. 15 shows the dis- 

 tribution of the chlorophyll bodies in the cells of a por- 

 tion 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. No Food can be formed Without Chlorophyll. 

 By the agency of chlorophyll, the chlorophyll bodies ab- 



