2 THE LIVING SUBSTANCE OF PLANTS 



functions, they all possess cell walls which contain during the 

 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 occur- 

 rence. Such plastids as contain a green pigment, chlorophyll, are 

 called chloroplastids or chloroplasts, and these produce the green 



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

 i), vacuole, ch, chloroplast. B, cell of carrot; ch, yellowish chromoplasts, n, 

 nucleus. C, reddish chromoplasts from rose hip. D, cells of Begonia; s, 

 starch grains, c, crystals of lime. E, leucoplast, I, of potato forming a starch 

 grain. 



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

 chromoplasts, contain red or yellow pigments that give the color 

 to many fruits and flowers, as the tomato, rose-hip, squash, nas- 

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



