94 CHLOROPHYLL-CORPUSCLES [CH. 



wall diffuse readily into the dead cell, whereas they would 

 have been kept back by the living protoplasm. 



The principal body in the cell for our purposes, how- 

 ever, is the chlorophyll-corpuscle. As the figure (Fig. 26) 

 shows, numbers of dark rounded bodies, much smaller than 

 the nucleus, are distributed evenly over the inner surface 

 of the cell-wall. Each of these is a small mass of proto- 

 plasmic substance, somewhat like a minute sponge, im- 

 pregnated with the green liquid known as chlorophyll, 

 or leaf-green. Each of these chlorophyll-corpuscles is 

 embedded in the living protoplasmic lining of the cell, 

 and is therefore in direct contact neither with the cell- 

 wall outside, nor with the cell-sap inside, and they present 

 a peculiar green translucent appearance under the micro- 

 scope almost comparable to emerald. 



These chlorophyll-corpuscles, moreover, are not mere 

 dead objects : they are capable of growth, division and 

 movements, and we have every reason for regarding them 

 as living bodies, though their life-activities are dependent 

 on the life of the cell. 



Experiments have shown that when the cells containing 

 these green chlorophyll-corpuscles are properly supplied 

 with water from the vessels of the venation, and with air 

 containing carbon-dioxide from the intercellular spaces, 

 and are at the same time exposed to fairly bright light 

 such as that of a sunny day, certain minute colourless 

 granules, shining in the green matrix like tiny pearls, 

 make their appearance in the substance of the chlorophyll- 

 corpuscles ; and the application of suitable tests to these 

 pearl-like bodies, as for instance iodine solution which 

 turns them blue, proves that these colourless granules 

 are grains of starch, a substance which contains carbon. 



If, however, any of the conditions above mentioned 

 are withheld if, for instance, the light is too feeble or 



