170 



Dynamic Theory. 



CHAPTER XXIY. 



CHLOROPHYL. 



Mention has been made of chlorophyl. This substance, like proto- 

 plasm, in general, is composed of oxygen, hydrogen, nitrogen and car- 

 bon, to which is added iron. Under the influence of sunlight it becomes 

 green. In the lower cellular plants it appears to be diffused throughout 

 the mass of the protoplasm of the cell, coloring it all more or less. 



In the higher vascular plants, however, the chlorophyl protoplasm 

 is separated from the rest ; a differentiation has taken place, and the 

 chlorophyl appears in the form of individually organized particles, or 

 granules from 1-1000 to 5-1000 of a millimeter in diameter. These or- 

 ganisms grow under proper conditions of nourishment and solar stimu- 

 lus, and at maturity reproduce and multiply by fission, each adult parti- 

 cle becoming two. These zoospores, under the influence of heat and 

 light, move about in the cells of the leaves of the plant. At night, and 



FIG. 90.- Chlorophyl Cells. 

 A. Part of a green leaf, 

 d. Chlorophyl cells containing green 



FIG. 90. 



B. Old Chlorophyl cells. 

 C. Chlorophyl cell in act of dividing, or 

 reproduction. 



protoplasm and granules of starch, 

 e. Protoplasm of the leaf cells. /.Beginning of the process. g. Ending. 



as the temperature decreases, they huddle together in the center of the 

 cells, but in daylight, and under increasing temperature, move out to- 

 ward the cell walls. Their color, when light is withdrawn, becomes 

 pale and yellowish, and if the light is withdrawn too long the organism 

 loses its power of growth and its substance is redissolved back into the 

 mass protoplasm of the plant. Although the body of the chlorophyl- 

 lian zoospore does not contain either potassium chlorate or potassium 

 nitrate yet one of these bodies must be present in the sap of the plant 

 in order that the functions of the chlorophyl may proceed properly. 

 We are reminded of the extreme sensibility to light, shown by these 



