CHLOROPLASTS. 73 



grains. After a little time the clearing effect of the glycerin 

 shows that the grains are not homogeneous, but contain a 

 denser, polygonal body looking like a crystal and known as a 

 crystalloid which varies in size, being often nearly as large as 

 the grain. Lying alongside of this is seen a globular body, 

 strongly refractive and composed of magnesium and calcium 

 phosphates and known as a glob old (Fig. 44). 



Add strong iodine solution to the section in glycerin. The 

 grains stain brown, especially deep in the crystalloid, indicat- 

 ing the proteid nature of the latter. The globoids remain 

 unstained. 



There is no blue coloration, showing the absence of starch. 



Mount a fresh section in water and watch the aleurone grains. 

 The ground substance soon swells and dissolves, leaving the 

 crystalloid standing out more distinct. After 

 a time this also swells and loses its angles and 

 finally disappears. Oil globules may also be 

 seen to collect and run out from the ruptured 

 cells. These have a refractive appearance, 

 being bounded by a dark band. 



If fresh sections be mounted in alcannin or 

 cyanin solution the oil globules will stain 

 after a time deep red or blue. Oil is a reserve 

 food for the plant, like starch and aleurone, 

 and is found in a great many seeds and spores, and gioboid 

 often in large quantity. 



Mount a section in dilute alkali (about 1 per cent.) and watch 

 a grain closely. All parts dissolve except the globoid. 



CHAPTER XVII. 



CHLOROPLASTS OR CHLOROPHYLL CORPUSCLES. 



When speaking of starch, it was noted what importance these 

 bodies are to the life of plants, and that without them plants 

 could not exist. They are the most important structural form 

 of protoplasm. They are the bodies which give the green color 

 to plants and are commonly rounded, oblong or flattened in 

 shape. An odd form is the spiral bands in Spirogyra (which 

 see). 



Chloroplasts are proteid in nature, having the power of 

 growth and division, and always closely associated with ordin- 

 ary protoplasm, and are hence to be regarded as part of the liv- 

 ing protoplasm. 



In many plants chloroplasts are small and difficult to study, 

 but in others they are easily studied. Most any moss, the 



