NUTRITION 



369 



sunlight, i.e. a narrow liar of light dispersed into a band of different 

 wave lengths, each group of waves produces its appropriate effeel and 

 we see a band of blending colors, 'lark red at one end, running through 

 ted, orange, yellow, green, blue, indigo, violet, and ending in the dark- 

 est violet. On interposing a leaf in the path of the light, there appear 

 across the spectrum dark strips due to the partial or complete stoppage 

 of the energy. Similar absorption hands, slightly displaced, are seen by 

 using in the same way an alcoholic solution of chlorophyll (tig. 648). 



a B C D E b F G h 



Fig. 648. — Absorption spectra: A, chlorophyll of Allium ursittum in alcohol; B, 

 chlorophyll of English ivy (II edera Helix) in alcohol; C, chlorophyll of Oscili 

 alcohol; D, carotin, i, 2, 3, 4, absorption bands of chlorophyllin; /, //, ///, absorp- 

 tion bands of carotin; EA, end absorption. The Intend broken lines mark tin- position 

 of the ['rincipal absorption lines of the solar spectrum (Fraunhofer lines); the numbered 

 solid lines form a si ale from which wave lengths (\) in millionths of a millimeter may be 

 found by adding a cipher; note the increasing dispersion from left (red) to right (violet). 

 — After Koiil. 



These absorption bands arc as follows: 1, in the red a wide black "tie. its wave 

 lengths i\i being 67c— 635 nn' ; 2, a narrower and less intense one in the orange, 

 X=622-5o; mm; 3, in the yellow, a band much lighter than a, and shading 

 out on the sides, \ ^S;-^,^ uix; ( , a faint band in the green, not always 

 to be seen, and probably due to decomposition products, X = 544-5,^0 mm- ( >r- 

 dinarily the other three blend into one, and there are no visible waves left beyond 

 the blue (X= 495-420). By very careful manipulation, using dilute solutions in- 

 stead of a leaf, they .an be distinguished, their limits not being sharply marked. 

 1 The exact location of the bands varies. 1 /xfi — 0.000001 nun. 

 C. B. .v C. no 1 \\y j 1 



