2 THE LIVING SUBSTANCE OF PLANTS 



life of the cell a substance termed protoplasm. This substance 

 resembles somewhat the white of an egg, being viscid and rather 

 tenacious. The protoplasm is not of uniform consistency. The 

 larger portion of it is finely granular and is called the cytoplasm 

 while a denser rounded part is termed the nucleus. Other bodies, 

 plastids, also denser than the cytoplasm are of common occurrence. 

 Such plastids as contain a green pigment, chlorophyll, are called 

 choroplastids or chloroplasts, and these produce the green color 





FIG. 2. Structure of the cell : A, cell of ditch-moss, Philotria; n, nucleus, 

 v, vacuole, ch, chloroplast. B, cell of carrot; ch, chromoplasts, n, nucleus. 

 C, chromoplasts from rose hip. D, cells of Begonia; s, starch grains, c, 

 crystals of lime. E, leucoplast, /_, of potato forming a starch grain. 



of the vegetation (Fig. 2, A). Still other plastids, the chromo- 

 plasts, contain red or yellow pigments that give the color to many 

 fruits and flowers, as the tomato, rose hip, squash, nasturtium, 

 etc. (Fig. 2, B, C). Colorless plastids, leucoplasts, often occur 

 in cells hidden from the light. One group of these leucoplasts 

 forms the starch that appears in underground storage organs as 



