MANUFACTURE OF ORGANIC FOOD 47 



got rid of and the position of separation of elements 

 re-established by the formation of complex com- 

 pounds deficient in it. How is this to be effected ? 

 The process requires an apparatus, and, further, 

 the expenditure of a large amount of energy. The 

 apparatus we have already seen is the chloroplast ; 

 the energy is derived from the sun. 



A beam of sunlight may be analysed by means 

 of a glass prism into rays of different colour. The 

 rays as observed in Nature give us the colours of the 

 rainbow namely, red, orange, yellow, green, blue, 



Aa? C 10 3)i 



FIG. 19. A, absorption spectrum of chlorophyll ; 

 B, solar spectrum. 



indigo, violet (Fig. 19). Let us now examine a solar 

 spectrum by means of a spectroscope and let us solar 

 also make an alcoholic solution of chlorophyll and spectrum, 

 introduce, in a flat-sided glass vessel, a thin film of 

 the solution between the source of light and the 

 prism ; we shall find that the previously continuous 

 coloured band is now interrupted by a dark band in 

 the red region, and also by paler bands in the yellow 

 and green, while the violet, indigo, and part of the 

 blue regions are almost completely wiped out. 

 We speak of this incomplete band of colour as the 

 absorption spectrum of chlorophyll, for we may Absorp- 

 assume that the chlorophyll absorbs some of the ^ p e n ctpum 

 sun's rays and allows others to pass through. What 



