CHAPTER rx 



CELL CONTENTS 



The cell contents of the plant are divided into two groups: 

 first, organic cell contents; and secondly, inorganic cell contents. 



The organic cell contents include plastids, starch grains, 

 mucilage, inulin, sugar, hesperidin, alkaloids, glucocides, tannin, 

 resin, and oils. 



CHLOROPHYLL 



The chloroplasts of the higher plants are green, and they 

 vary somewhat in size, but they have a similar structure and 

 form. 



Chloroplasts are mostly oval in longitudinal view and rounded 

 in cross-section view. Each chlorophyll grain has an extremely 

 thin outer wall, which encloses the protoplasmic substance, the 

 green granules, a green pigment (chlorophyll), and a yellow 

 pigment (xanthophyll). Frequently the wall includes starch, 

 oil drops, and protein crystals. 



Chloroplasts are arranged either in a regular peripheral 

 manner along the walls, or they are diffused throughout the 

 protoplast. 



The palisade cells of most leaves are packed with chlorophyll 

 grains. In the mesophyll cells the chlorophyll grains are not 

 so numerous, and they are arranged peripherally around the 

 innermost part of the wall. 



Chloroplasts multiply by fission — that is, each chloroplast 

 divides into two equal halves, each of which develops into a 

 normal chloroplast. 



Chlorophyll occurs in the paHsade, spongy parenchyma, and 

 guard cells of the leaf; in the collenchyma and parenchynia of 

 the cortex of the stems of herbs and of young woody stems, and, 

 under certain conditions, in rhizomes and roots exposed to 

 light. Almost without exception young seeds and fruits have 

 chlorophyll. 



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