CHLOROPHYLL; STARCH. 6y 



vaucheria, should be examined here if possible, in order to be- 

 come famihar with their form, since they will be studied later 

 under morphology (see chapters on oedogonium and vaucheria, 

 for the occurrence and form of these plants). The form of the 

 chlorophyll body found in cedogonium and vaucheria is that 

 which is common to many of the green algse, and also occurs in 

 the mosses, liverworts, ferns, and the higher plants. It is a 

 more or less rounded, oval, flattened body. 



159. Chlorophyll is a pigment which resides in the chloroplast. — That 

 the chlorophyll is a coloring substance which resides in the cliloroplastid, 

 and does not form the body itself, can be demonstrated by dissolving out the 

 chlorophyll when the framework of the chloroplastid is apparent. The 

 green parts of plants which have been placed for some time in alcohol lose 

 their green color. The alcohol at the same time becomes tinged with green. 

 In sectioning such plant tissue we find that the chlorophyll bodies, or chloro- 

 plastids as they are more properly called, are still intact, though the green 

 color is absent. From this we know that chlorophyll is a substance distinct 

 from that of the chloroplastid. 



160. Chlorophyll absorbs energy from sunlight for carbon conversion. — It 

 has been found by analysis with the spectroscope that chlorophyll absorbs cer- 

 tain of the rays of the sunlight. The energy which is thus obtained from 

 the sun, called kinetic energy, is supposed to act on the molecules of CO2 and 

 HjO, separating them into other molecules of C, H, and O, and that after a 

 series of complicated chemical changes starch is formed by the union of mole- 

 cules of carbon, oxygen, and hydrogen, the hydrogen and some of the oxygen 

 at least coming from the water in the cells of the plant. In thii process of 

 the reduction of the CO2 and the formation of starch there is a surplus of 

 oxygen, which accounts for the giving off of oxygen during the process. 



161. Eays of light concerned in carbon conversion. — If a solution of 

 chlorophyll be made, and light be passed through it, and this light be 

 examined with the spectroscope, there appear what are called absorption bands. 

 These are dark bands which lie across certain portions of the spectrum. 

 These bands lie in the red, orange, yellow, green, blue, and violet, but the 

 bands are stronger in the red, which shows that chlorophyll absorbs more of 

 the red rays of light than of the other rays. These are the rays of low 

 refrangibility. The kinetic energy derived by the absorption of these rays 

 of light is transferred into potential energy. That is, the molecule of CO2 is 

 broken up, and then by a different combination of certain elements starch is 

 formed.* 



* In the formation of starch during carbon conversion the separated mole- 

 cules from the carbon dioxide and water unite in such a way that carbon. 



