70 PHYSIOLOGY. 



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

 In sectioning such plant tissue we find lh.it the chlorophyll bodies, or chloro- 

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

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

 from that (\i the chloroplastid. 



146. Chlorophyll absorbs ener^ from sunlight for photosynthesis. —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, acts on the molecules of Cll^**., , separating 

 them into molecules of C, 11, and O. (When the C'( ',, from the air enters 

 the plant cell it immediately unites widi some of the water, iurming carbonic 

 acid = C1I„C*.^. ) Alter a series of cnmjdicaled chemical changes starch is 

 formed by the union cf carbon, oxygen, and hvdrogen. In this process of 

 the reduction of the CH„0, and the formation of starch there is a surplus of 

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



147. Bays of light concerned in photosynthesis. — If a solution of 

 chlorophyll be made, and light be p.issed tiirough it, and this light be 

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

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

 These bands lie in the red, (jrange, yellow, green, blue, and violet, l.iut the 

 l,ands are stronger in the red, whiidi shows that chlorophyll absorbs mure of 

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

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

 of light is transformed into potential energy. That is, the molecule of 

 CH.,0.j is l-roken up, and then by a different combination of certain elements 

 starch is formed,'^ 



148. Starch grains formed in the chloroplasts. — During photosynthesis the 

 stareh formed is deposited generally in small grains within the green chloro- 

 plast in the leaf. We can see this easilv b^' exivniining the leaves of some 

 moss like funaria which has been in the light, or in the (.hloroplasts of the 

 prothallia of ferns, etc. Starch grains mav also be formed in the chloro- 

 plasts from starch which was formed in some other part of the plant, but 



* In the formation of starch during photosynthesis the separated mole- 

 cules fvoni the carbon dioxide and water unite in such a "way that carbon, 

 hydrogen, and oxygen arc united into a molecule of starch, d his result is 

 usually represented by the following equation: C'O.-f H.O = CHoOd-Oo. 

 Then l')y ]-)olymcrization 6fCH^()) = Co^Ii/^e = gT'^^P^ sugar. Then 

 C,dl,,XV, - \\p = r,,H,.0;^ = starch. It is believed, however, that the 

 process is much more complicated than this, that several different com- 

 pounds arc forme*! before Stan li hnall)' appears, and that the foriuula for 

 Starrh is much higher numerically than is repre^ented by C.Tlj^O^. 



