NUTRITION 
3 6 9 
sunlight, i.e. a narrow bar of light dispersed into a band of different 
wave lengths, each group of waves produces its appropriate effect and 
We see a band of blending colors, dark red at one end, running through 
red, orange, yellow, green, blue, indigo, violet, and ending in the dark- 
est violet. On interposing a le^f 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 bands, slightly displaced, are seen by 
using in the same way an alcoholic solution of chlorophyll (fig. 648). 
FIG. 648. Absorption spectra: A, chlorophyll of Allium ursinum in alcohol; B, 
chlorophyll of English ivy (Hedera Helix) in alcohol; C, chlorophyll of Oscillatoria in 
alcohol; D, carotin, i, 2, 3, 4, absorption bands of chlorophyllin ; /, //, ///, absorp- 
tion bands of carotin; EA, end absorption. The lettered broken lines mark the position 
of the principal absorption lines of the solar spectrum (Fraunhofer lines); the numbered 
solid lines form a scale from which wave lengths (X) in millionths of a millimeter may be 
found by adding a cipher; note the increasing dispersion from left (red) to right (violet). 
After KOHL. 
These absorption bands are as follows: i, in the red a wide black one, its wave 
lengths (X) being 670-635 /*/i l ; 2, a narrower and less intense one in the orange, 
X = 622-597 fj-fj.; 3, in the yellow, a band much lighter than 2, and shading 
out on the sides, X = 587-565 w, 4, a faint band in the green, not always 
to be seen, and probably due to decomposition products, X = 544-53 o ytt/u. Or- 
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 can be distinguished, their limits not being sharply marked. 
1 The exact location of the bands varies, i /t/t = o.oooooi mm. 
